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exar corporation 48720 kato road, fremont ca, 94538 ? (510) 668-7000 ? fax (510) 668-7017 ? www.exar.com XR16V2652 high performance duart with 32-byte fifo may 2007 rev. 1.0.2 general description the XR16V2652 1 (v2652) is a high performance dual universal asynchronous receiver and transmitter (uart) with 32 byte tx and rx fifos. the device operates from 2.25 to 3.6 volts with 5 volt tolerant inputs and is pin-to-pin compatible to exar?s st16c2552, xr16l2552, xr16v2552 and xr16l2752. the v2652 register set is compatible to the st16c2552 and the xr16v2552. it supports the exar?s enhanced features of selectable fifo trigger level, automatic hardware (rts/cts) and software flow control and a complete modem interface. onboard registers provide the user with operational status and data error flags. an internal loopback capability allows system diagnostics. independent programmable baud rate generators are provided in each channel to select data rates up to 16 mbps at 3.3 volt with 4x sampling clock. the v2652 is available in 44-pin plcc and 32-pin qfn packages. n ote : 1 covered by u.s. patent #5,649,122 applications ? portable appliances ? telecommunication network routers ? ethernet network routers ? cellular data devices ? factory automation and process controls features ? 2.25 to 3.6 volt operation ? 5 volt tolerant inputs ? pin-to-pin compatible to exar?s xr16v2752 in the 44-plcc package ? two independent uart channels register set compatible to st16c2552 data rate of up to 16 mbps at 3.3 v and 12.5 mbps at 2.5 v with 4x sampling rate fractional baud rate generator transmit and receive fifos of 32 bytes selectable tx and rx fifo trigger levels automatic hardware (rts/cts) flow control automatic software (xon/xoff) flow control wireless infrared (irda 1.0) encoder/decoder automatic sleep mode full modem interface ? alternate function register ? device identification and revision ? crystal oscillator or external clock input ? crystal oscillator (up to 32 mhz) or external clock (up to 64 mhz) input ? 44-plcc and 32-qfn packages f igure 1. XR16V2652 b lock d iagram xtal1 xtal2 crystal osc/buffer txa, rxa, dtra#, dsra#, rtsa#, dtsa#, cda#, ria#, op2a# 8-bit data bus interface uart channel a 32 byte tx fifo brg ir endec tx & rx uart regs 2.25 to 3.6 volt vcc gnd * 5 volt tolerant inputs txb, rxb, dtrb#, dsrb#, rtsb#, ctsb#, cdb#, rib#, op2b# uart channel b (same as channel a) a2:a0 d7:d0 cs# chsel inta intb iow# ior# reset txrdya# txrdyb# rxrdya# rxrdyb# 32 byte rx fifo
XR16V2652 2 high performance duart with 32-byte fifo rev. 1.0.2 f igure 2. p in o ut a ssignment ordering information p art n umber p ackage o perating t emperature r ange d evice s tatus XR16V2652il32 32-qfn -40c to +85c active XR16V2652ij 44-lead plcc -40c to +85c active 32 31 30 29 1 2 3 4 5 6 7 8 24 23 22 21 20 19 11 12 13 14 15 16 9 10 d5 d6 d7 a0 xtal1 xtal2 a1 a2 chsel cs# iow# reset rtsb# ior# rxb txb rxa txa rtsa# inta gnd nc nc d4 d3 d2 d1 d0 vcc ctsa# XR16V2652 32-pin qfn 28 27 26 25 18 17 intb ctsb# 6 5 4 3 2 1 44 43 42 41 40 7 8 9 10 11 12 13 14 15 16 17 39 38 37 36 35 34 33 32 31 30 29 18 19 20 21 22 23 24 25 26 27 28 d5 d6 d7 a0 xtal1 gnd xtal2 a1 a2 chsel intb rxa txa dtra# rtsa# mfa# inta vcc txrdyb# rib# cdb# dsrb# cs# mfb# iow# reset gnd rtsb# ior# rxb txb dtrb# ctsb# d4 d3 d2 d1 d0 txrdya# vcc ria# cda# dsra# ctsa# XR16V2652 44-pin plcc
XR16V2652 3 rev. 1.0.2 high performance duart with 32-byte fifo pin descriptions pin description n ame 32-qfn p in # 44-plcc p in # t ype d escription data bus interface a2 a1 a0 7 6 3 15 14 10 i address data lines [2:0]. these 3 address lines select one of the inter - nal registers in uart channel a/b during a data bus transaction. d7 d6 d5 d4 d3 d2 d1 d0 2 1 32 31 30 29 28 27 9 8 7 6 5 4 3 2 i/o data bus lines [7:0] (bidirectional). ior# 14 24 i input/output read strobe (active low) . the falling edge instigates an internal read cycle and retrieves the data byte from an internal register pointed to by the address lines [a2:a0]. the data byte is placed on the data bus to allow the host processor to read it on the rising edge. iow# 11 20 i input/output write strobe (active low). the falling edge instigates an internal write cycle and the rising edge transfers the data byte on the data bus to an internal register pointed by the address lines. cs# 10 18 i uart chip select (active low). this function selects channel a or b in accordance with the logical state of t he chsel pin. this allows data to be transferred between the user cpu and the v2652. chsel 8 16 i channel select - uart channel a or b is selected by the logical state of this pin when the cs# pin is a logic 0. a logic 0 on the chsel selects the uart channel b while a logic 1 selects uart channel a. normally, chsel could just be an address line from the user cpu such as a4. bit-0 of the alternate function regi ster (afr) can temporarily override chsel function, allowing the user to write to both channel register simultaneously with one write cycle when cs# is low. it is especially useful during the initialization routine. inta 21 34 o uart channel a interrupt output (a ctive high). a high indicates chan - nel a is requesting for service. for more details, see figures 17 - 22 . intb 9 17 o uart channel b interrupt output (a ctive high). a high indicates chan - nel b is requesting for service. for more details, see figures 17 - 22 . txrdya# - 1 o uart channel a transmitter ready (active low). the output provides the tx fifo/thr status for transmit channel a. see table 2 . txrdyb# - 32 o uart channel b transmitter ready (active low). the output provides the tx fifo/thr status for transmit channel b. see ta b l e 2 . modem or serial i/o interface txa 23 38 o uart channel a transmit data or infrared encoder data. standard transmit and receive interface is e nabled when mcr[6] = 0. in this mode, the tx signal will be high during reset or idle (no data). infrared irda transmit and receive interface is enabled when mcr[6] = 1. in the infrared mode, the inactive state (no data) for the infrared encoder/ decoder interface is low. if it is not used, leave it unconnected.
XR16V2652 4 high performance duart with 32-byte fifo rev. 1.0.2 rxa 24 39 i uart channel a receive data or infrared receive data. normal receive data input must idle high. the infrared receiver pulses typically idles low but can be inverted by software control prior going in to the decoder, see mcr[6]. if this pin is not used, tie it to vcc or pull it high via a 100k ohm resistor. rtsa# 22 36 o uart channel a request-to-send (active low) or general purpose out - put. this output must be asserted pr ior to using auto rts flow control, see efr[6], mcr[1] and ier[6]. ctsa# 25 40 i uart channel a clear-to-send (active lo w) or general purpose input. it can be used for auto cts flow cont rol, see efr[7], and ier[7]. this input should be connected to vcc when not used. dtra# - 37 o uart channel a data-terminal-ready (active low) or general purpose output. if this pin is not used, leave it unconnected. dsra# - 41 i uart channel a data-set-ready (active low) or general purpose input. this input should be connected to vcc when not used. this input has no effect on the uart. cda# - 42 i uart channel a carrier-detect (active low) or general purpose input. this input should be connected to vcc when not used. this input has no effect on the uart. ria# - 43 i uart channel a ring-indicator (active low) or general purpose input. this input should be connected to vcc when not used. this input has no effect on the uart. mfa# - 35 o multi-function output channel a. this output pin can function as the op2a#, baudouta#, or rxrdya# pin. one of th ese output signal functions can be selected by the user programmable bits 1-2 of the alternate function register (afr). these signal functions are described as follows: 1) op2a# - when op2a# (active low) is selected, the mf# pin is low when mcr bit-3 is set to a logic 1 (see mcr bit-3). mcr bit-3 defaults to a logic 0 condition after a reset or power-up. 2) baudouta# - when baudouta# function is selected, the baud rate clock output is available at this pin. 3) rxrdya# - rxrdya# (active low) is intended for monitoring block data transfers. see ta b l e 2 for more details. txb 16 26 o uart channel b transmit data or infrared encoder data. standard transmit and receive interface is enabled when mcr[6] = 0. in this mode, the tx signal will be high during reset or idle (no data). infrared irda transmit and receive interface is enabled when mcr[6] = 1. in the infrared mode, the inactive state (no data) for the infrared encoder/ decoder interface is low. if it is not used, leave it unconnected. rxb 15 25 i uart channel b receive data or infrared receive data. normal receive data input must idle high. the infrared receiver pulses typically idles low but can be inverted by software control prior going in to the decoder, see mcr[6]. if this pin is not used, tie it to vcc or pull it high via a 100k ohm resistor. rtsb# 13 23 o uart channel b request-to-send (active low) or general purpose out - put. this port must be asserted prio r to using auto rts flow control, see efr[6], mcr[1] and ier[6]. pin description n ame 32-qfn p in # 44-plcc p in # t ype d escription
XR16V2652 5 rev. 1.0.2 high performance duart with 32-byte fifo pin type: i=input, o=output, i/o= input/output, od=output open drain. ctsb# 17 28 i uart channel b clear-to-send (active lo w) or general purpose input. it can be used for auto cts flow cont rol, see efr[7], and ier[7]. this input should be connected to vcc when not used. dtrb# - 27 o uart channel b data-terminal-ready (active low) or general purpose output. if this pin is not used, leave it unconnected. dsrb# - 29 i uart channel b data-set-ready (active low) or general purpose input. this input should be connected to vcc when not used. this input has no effect on the uart. cdb# - 30 i uart channel b carrier-detect (active low) or general purpose input. this input should be connected to vcc when not used. this input has no effect on the uart. rib# - 31 i uart channel b ring-indicator (active low) or general purpose input. this input should be connected to vcc when not used. this input has no effect on the uart. mfb# - 19 o multi-function output channel b. this output pin can function as the op2b#, baudoutb#, or rxrdyb# pi n. one of these output signal functions can be selected by the user programmable bits 1-2 of the alternate function register (afr). these signal functions are described as follows: 1) op2b# - when op2b# (active low) is selected, the mf# pin is low when mcr bit-3 is set high (see mcr bit-3). mcr bit-3 defaults to a logic 0 condition after a reset or power-up. 2) baudoutb# - when baudoutb# function is selected, the baud rate clock output is available at this pin. 3) rxrdyb# - rxrdyb# (active low) is intended for monitoring block data transfers. see ta b l e 2 for more details. ancillary signals xtal1 4 11 i crystal or external clock input. xtal2 5 13 o crystal or buffered clock output. reset 12 21 i reset (active high) - a longer than 40 ns high pulse on this pin will reset the internal registers and all outputs. the uart transmitter output will be held high, the receiver input will be ignored and outputs are reset during reset period (see ta b l e 15 ). vcc 26 44, 33 pwr 2.25 to 3.6v power supply. all input pins are 5v tolerant. gnd 20 22, 12 pwr power supply common, ground. gnd center pad n/a pwr the center pad on the backside of the 32-qfn package is metallic and should be connected to gnd on the pcb. the thermal pad size on the pcb should be the approximate size of this center pad and should be solder mask defined. the solder mask opening should be at least 0.0025" inwards from the edge of the pcb thermal pad. nc 18, 19 - - no connect. pin description n ame 32-qfn p in # 44-plcc p in # t ype d escription
XR16V2652 6 high performance duart with 32-byte fifo rev. 1.0.2 1.0 product description the XR16V2652 (v2652) integrates the functions of 2 enhanced 16c550 universal asynchronous receiver and transmitter (uart). each uart is independently c ontrolled having its own set of device configuration registers. the configuration registers set is 16550 ua rt compatible for control, status and data transfer. additionally, each uart channel has 32-bytes of tran smit and receive fifos, automatic rts/cts hardware flow control, automatic xon/xoff and special character so ftware flow control, select able transmit and receive fifo trigger levels, infrared encoder and decoder (irda ver 1.0), programmable fractional baud rate generator with a prescaler of divide by 1 or 4, and data rate up to 16 mbps with 4x sampling clock rate. the XR16V2652 is a 2.25 to 3.6v device with 5 volt tolerant inputs. the v2652 is fabr icated with an advanced cmos process. enhanced features the v2652 duart provides a solution that supports 32 bytes of transmit and receive fifo memory, instead of 16 bytes in the st16c2550 or one byte in the st16c2450. the v2652 is designed to work with low supply voltage and high performance data communication systems, that require fast data processing time. increased performance is realized in the v2652 by the larger tr ansmit and receive fifos, fifo trigger level control and automatic flow control mechanism. this allows the external processor to handle more networking tasks within a given time. for example, the st16c2550 with a 16 by te fifo, unloads 16 bytes of receive data in 1.53 ms (this example uses a character length of 11 bits, including start/stop bits at 115.2 kbps). this means the external cpu will have to service the re ceive fifo at 1.53 ms intervals. howeve r with the 32 byte fifo in the v2652, the data buffer will not require unloading/loading for 3.06 ms. this in creases the service interval giving the external cpu additional time for other applications and reducing the overall uart interrupt servicing time. in addition, the selectable fifo level trigger interrupt and automatic hardware/software flow control is uniquely provided for maximum data throughput performance espec ially when operating in a multi-channel system. the combination of the above greatly reduces the cpu?s bandwidth requirement, increases performance, and reduces power consumption. data rate the v2652 is capable of operation up to 16 mbps at 3. 3v and 12.5 mbps at 2.5v with 4x sampling clock rate. the device can operate with an external 32 mhz crystal at 2.5v on pins xtal1 and xtal2, or external clock source of up to 64 mhz on xtal1 pin. with a typical crystal of 14.7456 mhz and through a software option, the user can set the prescaler bit for data rates of up to 3.68 mbps. the rich feature set of the v2652 is available through th e internal registers. automatic hardware/software flow control, selectable transmit and re ceive fifo trigger levels, programmable tx and rx baud rates, infrared encoder/decoder interface, modem interface controls, and a sleep mode are all standard features. following a power on reset or an external reset, the v2652 is software compatible wit h previous generation of uarts, 16c450, 16c550 and 16c650a.
XR16V2652 7 rev. 1.0.2 high performance duart with 32-byte fifo 2.0 functional descriptions 2.1 cpu interface the cpu interface is 8 data bits wide with 3 address li nes and control signals to execute data bus read and write transactions. the v2652 data interface supports the intel compatible types of cp us and it is compatible to the industry standard 16c550 uart. no clock (oscillato r nor external clock) is required to operate a data bus transaction. each bus cycle is asynchronous usi ng cs#, ior# and iow# signals. both uart channels share the same data bus for host operations. the data bus interconnections are shown in figure 3 2.2 5-volt tolerant inputs the v2652 can accept up to 5v inputs even when operati ng at 3.3v or 2.5v. but note that if the v2652 is operating at 2.5v, its v oh may not be high enough to meet the requirements of the v ih of a cpu or a serial transceiver that is operating at 5v. 2.3 device reset the reset input resets the internal registers and the seri al interface outputs in both channels to their default state (see table 15 ). an active high pulse of l onger than 40 ns duration will be required to activate the reset function in the device. 2.4 device identification and revision the XR16V2652 provides a device identification code and a device revision code to distinguish the part from other devices and revisions. to read the identification code from the part, it is required to set the baud rate generator regist ers dll and dlm both to 0x00 (dld = 0xxx). now reading the content of the dlm will provide 0x06 for the XR16V2652 and reading the content of dll will pr ovide the revision of the part; for example, a reading of 0x01 means revision a. 2.5 channel a and b selection the uart provides the user with the capability to bi-directionally tr ansfer information be tween an external cpu and an external serial communication device. a logic 0 on chip select pin (cs#) allows the user to select the uart and then using the channel select (chsel) pin, the user can select channel a or b to configure, send transmit data and/or unload receive data to/from th e uart. individual channel select functions are shown in table 1 . f igure 3. XR16V2652 d ata b us i nterconnections vcc vcc (op2a#) dsra# ctsa# rtsa# dtra# rxa txa ria# cda# (op2b#) dsrb# ctsb# rtsb# dtrb# rxb txb rib# cdb# gnd a0 a1 a2 uart_cs# uart_chsel ior# iow# d0 d1 d2 d3 d4 d5 d6 d7 a0 a1 a2 cs# chsel d0 d1 d2 d3 d4 d5 d6 d7 ior# iow# uart channel a uart channel b uart_intb uart_inta intb inta (rxrdya#) txrdya# (rxrdya#) txrdya# (rxrdyb#) txrdyb# (rxrdyb#) txrdyb# uart_reset reset serial interface of rs-232, rs-422 serial interface of rs-232, rs-422 (baudoutb#) (baudouta#) pins in parentheses become available through the mf# pin. mf# a/b becomes rxrdy# a/b when afr[2:1] = '10'. mf# a/b becomes op2 # a/b when afr[2:1] = '00'. mf# a/b becomes baudout# a/b when afr[1:0] = '01'.
XR16V2652 8 high performance duart with 32-byte fifo rev. 1.0.2 2.6 channel a and b internal registers each uart channel in the v2652 has a set of enhanced registers for cont rolling, monitoring and data loading and unloading. the configuration register set is compat ible to those already available in the standard single 16c550 and dual st16c2550. these r egisters function as data holding regi sters (thr/rhr), interrupt status and control registers (isr/ier), a fi fo control register (fcr), receive lin e status and control registers (lsr/ lcr), modem status and control regist ers (msr/mcr), programmable data rate (clock) divisor registers (dll/ dlm/dld), and a user accessible scratchpad register (spr). beyond the general 16c2550 features and capabilities, the v2652 offers enhanced feature registers (efr, xon/xoff 1, xon/xoff 2) that provide automatic rts and cts hardware flow control and xon/xoff software flow control. all the register functions are discussed in full detail later in ?section 3.0, uart internal registers? on page 21 . 2.7 dma mode the device does not support direct memory access. th e dma mode (a legacy term) in this document does not mean ?direct memory access? but refers to data block transfer operation. the dma mode affects the state of the rxrdy# a/b and txrdy# a/b output pins. the transmit and receive fifo trigger levels provide additional flexibility to the user for block mode operation. the lsr bits 5- 6 provide an indication when the transmitter is empty or has an empty location(s) for more data. the user can optionally operate the transmit and receive fifo in the dma mode (fcr bit-3=1). when the transmit and receive fifo are enabled and the dma mode is disabled (fcr bit-3 = 0), the v2652 is placed in single-character mode for data transmit or receive operation. when dma mode is enabled (fcr bit-3 = 1), the user takes advantage of block mode operation by loading or unloading the fifo in a block sequence determined by the selected trigger le vel. in this mode, the v2652 sets the txrdy# pin when the transmit fifo becomes full, and sets the rxrdy# pin when the receive fifo becomes empty. the following table shows their behavior. also see figures 17 through 22 . t able 1: c hannel a and b s elect cs# chsel f unction 1 x uart de-selected 0 1 channel a selected 0 0 channel b selected t able 2: txrdy# and rxrdy# o utputs in fifo and dma m ode p ins fcr bit -0=0 (fifo d isabled ) fcr b it -0=1 (fifo e nabled ) fcr bit-3 = 0 (dma mode disabled) fcr bit-3 = 1 (dma mode enabled) rxrdy# a/b low = 1 byte. high = no data. low = at least 1 byte in fifo. high = fifo empty. high to low transition when fifo reaches the trigger level, or time-out occurs. low to high transition when fifo empties. txrdy# a/b low = thr empty. high = byte in thr. low = fifo empty. high = at least 1 byte in fifo. low = fifo has at least 1 empty location. high = fifo is full.
XR16V2652 9 rev. 1.0.2 high performance duart with 32-byte fifo 2.8 inta and intb outputs the inta and intb interrupt output changes according to the operating mode and enhanced features setup. table 3 and 4 summarize the operating behavior for the transmitter and receiver. also see figures 17 through 22 . 2.9 crystal oscillator or external clock input the v2652 includes an on-chip oscillator (xtal1 and xtal2) to prod uce a clock for both ua rt sections in the device. the cpu data bus does not r equire this clock for bus operation. the crystal oscillator provides a system clock to the baud rate generators (brg) section found in each of the uart. xtal1 is the input to the oscillator or external clock buffer input with xtal 2 pin being the output. fo r programming details, see ? ?section 2.10, programmable baud rate gene rator with fractional divisor? on page 10 .? t able 3: inta and intb p ins o peration for t ransmitter fcr b it -0 = 0 (fifo d isabled ) fcr b it -0 = 1 (fifo e nabled ) inta/b pin low = a byte in thr high = thr empty low = fifo above trigger level high = fifo below trigger level or fifo empty inta/b pin low = a byte in thr high = transmitter empty low = fifo above trigger level high = fifo below trigger level or transmitter empty t able 4: inta and intb p in o peration f or r eceiver fcr b it -0 = 0 (fifo d isabled ) fcr b it -0 = 1 (fifo e nabled ) inta/b pin low = no data high = 1 byte low = fifo below trigger level high = fifo above trigger level f igure 4. t ypical c rystal c onnections c1 22-47pf c2 22-47pf y1 1.8432 mhz to 24 mhz r1 0-120 (optional) r2 500k - 1m xtal1 xtal2
XR16V2652 10 high performance duart with 32-byte fifo rev. 1.0.2 the on-chip oscillator is designed to use an industry standard micropro cessor crystal (p arallel resonant, fundamental frequency with 10-22 pf capacitance load, esr of 20-120 ohms and 100 ppm frequency tolerance) connected externally between the xtal1 and xtal2 pins (see figure 4 ). the programmable baud rate generator is capable of operating with a crystal osc illator frequency of up to 32 mhz at 2.5v. however, with an external clock input on xtal1 pin, it can extend its operation up to 64 mhz (16 mbps serial data rate) at 3.3v with an 4x sampling rate. for further reading on the o scillator circuit please se e the application note dan108 on the exar web site at http://www.exar.com. 2.10 programmable baud rate generator with fractional divisor each uart has its own baud rate generator (brg) with a prescaler for the transmitter and receiver. the prescaler is controlled by a software bit in the mcr register. the mcr register bit-7 sets the prescaler to divide the input crystal or external clock by 1 or 4. the outpu t of the prescaler clocks to the brg. the brg further divides this clock by a programmable divisor between 1 an d (216 - 0.0625) in increments of 0.0625 (1/16) to obtain a 16x or 8x sampling clock of the serial data rate . the sampling clock is used by the transmitter for data bit shifting and receiver for data sampling. the brg divisor (dll, dlm and dld registers) defaults to the value of ?1? (dll = 0x01, dlm = 0x00 and dld = 0x00) upon reset. therefore, the brg must be programmed during initialization to the operating data rate. the dll and dlm registers provide the integer part of the divisor and the dld register provides the fractional part of the dvis ior. only the four lower bits of the dld are implemented and they are used to select a value from 0 (for setting 0000) to 0.9375 or 15/16 (for setting 1111). programming the baud rate generator registers dl l, dlm and dld provides the capab ility for selecting the operating data rate. table 5 shows the standard data rates available with a 24 mhz crystal or external clock at 16x clock rate. if the prescaler is used (mcr bit- 7 = 1), the output data rate will be 4 times less than that shown in table 5 . at 8x sampling rate, these data rates would double. and at 4x sampling rate, they would quadruple. also, when using 8x sampling mode, please note that the bit-time will have a jitter (+/- 1/16) whenever the dld is non-zero and is an odd number. when using a non-standard data rate crystal or external clock, the divisor value can be calculated with the following equation(s): the closest divisor that is obtainable in the v2652 can be calculated using the following formula: in the formulas above, please note that: trunc (n) = integer part of n. for example, trunc (5.6) = 5. round (n) = n rounded towards the cl osest integer. for example, roun d (7.3) = 7 and round (9.9) = 10. a >> b indicates right shifting the value ?a? by ?b? number of bits. for example, 0x78a3 >> 8 = 0x0078. required divisor (decimal) =(xtal1 clock frequency / prescaler) / (serial data rate x 16), with 16x mode dld[5:4]=?00? required divisor (decimal) = (xtal1 clock frequency / prescaler / (serial data rate x 8), with 8x mode dld[5:4]=?01? required divisor (decimal) = (xtal1 clock frequency / prescaler / (serial data rate x 4), with 4x mode dld[5:4]=?10? round( (required divisor - trunc(required divisor ) )*16)/16 + trunc( required divisor), where dlm = trunc(required divisor) >> 8 dll = trunc(required divisor) & 0xff dld = round( (required divisor -trunc(required divisor) )*16)
XR16V2652 11 rev. 1.0.2 high performance duart with 32-byte fifo f igure 5. b aud r ate g enerator t able 5: t ypical data rates with a 24 mh z crystal or external clock at 16x s ampling required output data rate d ivisor for 16x clock (decimal) d ivisor o btainable in v2652 dlm p rogram v alue (hex) dll p rogram v alue (hex) dld p rogram v alue (hex) d ata e rror r ate (%) 400 3750 3750 e a6 0 0 2400 625 625 2 71 0 0 4800 312.5 312 8/16 1 38 8 0 9600 156.25 156 4/16 0 9c 4 0 10000 150 150 0 96 0 0 19200 78.125 78 2/16 0 4e 2 0 25000 60 60 0 3c 0 0 28800 52.0833 52 1/16 0 34 1 0.04 38400 39.0625 39 1/16 0 27 1 0 50000 30 30 0 1e 0 0 57600 26.0417 26 1/16 0 1a 1 0.08 75000 20 20 0 14 0 0 100000 15 15 0 f 0 0 115200 13.0208 13 0 d 0 0.16 153600 9.7656 9 12/16 0 9 c 0.16 200000 7.5 7 8/16 0 7 8 0 225000 6.6667 6 11/16 0 6 b 0.31 230400 6.5104 6 8/16 0 6 8 0.16 250000 6 6 0 6 0 0 300000 5 5 0 5 0 0 400000 3.75 3 12/16 0 3 c 0 460800 3.2552 3 4/16 0 3 4 0.16 500000 3 3 0 3 0 0 750000 2 2 0 2 0 0 921600 1.6276 1 10/16 0 1 a 0.16 1000000 1.5 1 8/16 0 1 8 0 xtal1 xtal2 crystal osc/ buffer mcr bit-7=0 (default) mcr bit-7=1 dll, dlm and dld registers prescaler divide by 1 prescaler divide by 4 16x or 8x or 4x sampling rate clock to transmitter and receiver to other channel fractional baud rate generator logic
XR16V2652 12 high performance duart with 32-byte fifo rev. 1.0.2 2.11 transmitter the transmitter section comprises of an 8-bit transmit shift register (tsr) and 32 bytes of fifo which includes a byte-wide transmit holding register (thr) . tsr shifts out every data bit with the 16x/8x/4x internal clock. a bit time is 16/8/4 clock periods (see dld). the transmitter sends the start-bit followed by the number of data bits, inserts the proper parity-bit if enabl ed, and adds the stop-bit(s). the status of the fifo and tsr are reported in the line status register (lsr bit-5 and bit-6). 2.11.1 transmit holding re gister (thr) - write only the transmit holding register is an 8-bit register pr oviding a data interface to the host processor. the host writes transmit data byte to the thr to be converted in to a serial data stream including start-bit, data bits, parity-bit and stop-bit(s). the least-si gnificant-bit (bit-0) becomes first data bit to go out. the thr is the input register to the transmit fifo of 32 bytes when fifo operation is enabl ed by fcr bit-0. every time a write operation is made to the thr, the fifo data pointer is automatically bumped to the next sequential data location. 2.11.2 transmitter operation in non-fifo mode the host loads transmit data to thr one character at a time. the thr empty flag (lsr bit-5) is set when the data byte is transferred to tsr. thr flag can generate a tr ansmit empty interrupt (isr bit-1) when it is enabled by ier bit-1. the tsr flag (lsr bit-6) is set when tsr beco mes completely empty. 2.11.3 transmitter operation in fifo mode the host may fill the transmit fifo with up to 32 bytes of transmit data. t he thr empty flag (lsr bit-5) is set whenever the fifo is empty. the thr empty flag can ge nerate a transmit empty interrupt (isr bit-1) when the amount of data in the fifo falls below its programmed tr igger level. the transmit em pty interrupt is enabled by ier bit-1. the tsr flag (lsr bit-6) is set when tsr/fifo becomes empty. f igure 6. t ransmitter o peration in non -fifo m ode transmit holding register (thr) transmit shift register (tsr) data byte l s b m s b thr interrupt (isr bit-1) enabled by ier bit-1 txnofifo1 16x or 8x or 4x clock ( dld[5:4] )
XR16V2652 13 rev. 1.0.2 high performance duart with 32-byte fifo 2.12 receiver the receiver section contains an 8-bit receive shift register (rsr) and 32 bytes of fifo which includes a byte-wide receive holding register (rhr). the rsr uses the 16x/8x/4x clock (dld[5:4]) for timing. it verifies and validates every bit on the incoming character in the middle of each data bit. on the falling edge of a start or false start bit, an internal receiver counter starts counting at the 16x/8x/4x clock rate. after 8 clocks (or 4 if 8x or 2 if 4x) the start bit pe riod should be at the center of the start bit. at this time the start bit is sampled and if it is still a logic 0 it is validated. evaluating the start bit in this manner prevents the receiver from assembling a false character. the rest of the data bits and stop bits are sampled and validated in this same manner to prevent false framing. if th ere were any error(s), they are reported in the lsr register bits 2-4. upon unloading the receive data byte from rhr, the rece ive fifo pointer is bumped and the error tags are immediately updated to reflect the status of the data byte in rhr register. rhr can generate a receive data ready interrupt upon receiving a character or delay unti l it reaches the fifo trigger level. furthermore, data delivery to the host is guaranteed by a receive data read y time-out interrupt when data is not received for 4 word lengths as defined by lcr[1:0] plus 12 bits time. this is equivalent to 3.7-4.6 character times. the rhr interrupt is enabled by ier bit-0. 2.12.1 receive holding register (rhr) - read-only the receive holding register is an 8-bit register that holds a receive data byte from the receive shift register. it provides the receive data interface to the host processor. the rhr register is part of the receive fifo of 32 bytes by 11-bits wide, the 3 extra bits are fo r the 3 error tags to be reported in lsr register. when the fifo is enabled by fcr bit-0, the rhr contains th e first data character received by the fifo. after the rhr is read, the next character byte is loaded into the rhr and the errors associated with the current data byte are immediately updated in the lsr bits 2-4. f igure 7. t ransmitter o peration in fifo and f low c ontrol m ode transmit data shift register (tsr) transmit data byte thr interrupt (isr bit-1) falls below the programmed trigger level and then when becomes empty. fifo is enabled by fcr bit-0=1 transmit fifo 16x or 8x or 4x clock (dld[5:4]) auto cts flow control (cts# pin) auto software flow control flow control characters (xoff1/2 and xon1/2 reg.) txfifo1
XR16V2652 14 high performance duart with 32-byte fifo rev. 1.0.2 f igure 8. r eceiver o peration in non -fifo m ode f igure 9. r eceiver o peration in fifo and a uto rts f low c ontrol m ode receive d ata shift register (rsr) receive d ata byte and errors rhr interrupt (isr bit-2) receive data h olding r egister (rhr) rxfifo1 16x or 8x or 4x clock ( dld[5:4] ) r eceive d ata characters d ata bit validation error tags in lsr bits 4:2 receive data shift register (rsr) rxfifo1 16x or 8x or 4x clock ( dld[5:4] ) error tags (32-sets) error tags in lsr bits 4:2 receive data characters data bit validation receive data fifo receive data receive data byte and errors rhr interrupt (isr bit-2) programmed for desired fifo trigger level. fifo is enabled by fcr bit-0=1 rts# de-asserts when data fills above the flow control trigger level to suspend remote transmitter. enable by efr bit-6=1, mcr bit-1. rts# re-asserts when data falls below the flow control trigger level to restart remote transmitter. enable by efr bit-6=1, mcr bit-1. 32 bytes by 11-bit wide fifo fifo trigger=16 data falls to 8 data fills to 24 example : - rx fifo trigger level selected at 16 bytes (see note below)
XR16V2652 15 rev. 1.0.2 high performance duart with 32-byte fifo 2.13 auto rts (hardware) flow control automatic rts hardware flow control is used to prevent data overrun to the local receiver fifo. the rts# output is used to request remote unit to suspend/r esume data transmission. the auto rts flow control features is enabled to fit specific application requirement (see figure 10 ): ? enable auto rts flow control using efr bit-6. ? the auto rts function must be started by asserting rts# output pin (mcr bit-1 to logic 1 after it is enabled). if using the auto rts interrupt: ? enable rts interrupt through ier bit-6 (after setting efr bit-4). the uart issues an interrupt when the rts# pin makes a transition from low to high: isr bit-5 will be set to logic 1. 2.14 auto rts hysteresis the v2652 has a new feature that prov ides flow control trigger hysteresis while maintaining compatibility with the xr16c850, st16c650a and st16c550 family of uarts. with the auto rts functi on enabled, an interrupt is generated when the receive fifo reaches the selected rx tri gger level. the rts# pin will not be forced high (rts off) until the receive fifo reaches one trigger level above the selected trigger level in the trigger table ( table 11 ). the rts# pin will return low after the rx fifo is unloaded to one le vel below the selected trigger level. under the above described conditions, the v2652 will continue to accept data until the receive fifo gets full. the auto rts function is initiated wh en the rts# output pin is asserted low (rts on). 2.15 auto cts flow control automatic cts flow control is used to prevent data overrun to the remote receiver fifo. the cts# input is monitored to suspend/restart the local transmitter. the aut o cts flow control feature is selected to fit specific application requirement (see figure 10 ): ? enable auto cts flow control using efr bit-7. if using the auto cts interrupt: ? enable cts interrupt through ier bit-7 (after setting efr bit-4). the uart issues an interrupt when the cts# pin is de-asserted (high): is r bit-5 will be set to 1, and uart will suspend transmission as soon as the stop bit of the character in process is shifted ou t. transmission is resumed after the cts# input is re- asserted (low), indicating more data may be sent. t able 6: a uto rts (h ardware ) f low c ontrol r x t rigger l evel int p in a ctivation rts# d easserted (h igh ) (c haracters in r x fifo) rts# a sserted (l ow ) (c haracters in r x fifo) 8 8 16 0 16 16 24 8 24 24 28 16 28 28 28 24
XR16V2652 16 high performance duart with 32-byte fifo rev. 1.0.2 f igure 10. a uto rts and cts f low c ontrol o peration the local uart (uarta) starts data transfer by asserting rtsa# (1). rtsa# is normally connected to ctsb# (2) of remote uart (uartb). ctsb# allows its transmitter to se nd data (3). txb data arrives and fills uarta receive fifo (4). when rxa data fills up to its receive fifo trigger le vel, uarta activates its rxa data ready interrupt (5) and con - tinues to receive and put data into it s fifo. if interrupt service latency is l ong and data is not being unloaded, uarta monitors its receive data fill level to match the upper th reshold of rts delay and de-assert rtsa# (6). ctsb# follows (7) and request uartb transmitter to suspend data transfer. ua rtb stops or finishes sending the data bits in its trans - mit shift register (8). when receive fifo data in uarta is unloaded to match the lower threshold of rts delay (9), uarta re-asserts rtsa# (10), ctsb# recognizes the change (11) and restarts its transmitter and data flow again until next receive fifo trigger (12). this same event applies to the reverse direction when uarta sends data to uartb with rtsb# and ctsa# controlling the data flow. rtsa# ctsb# rxa txb transmitter receiver fifo trigger reached auto rts trigger level auto cts monitor rtsa# txb rxa fifo ctsb# remote uart uartb local uart uarta on off on suspend restart rts high threshold data starts on off on assert rts# to begin transmission 1 2 3 4 5 6 7 receive data rts low threshold 9 10 11 receiver fifo trigger reached auto rts trigger level transmitter auto cts monitor rtsb# ctsa# rxb txa inta (rxa fifo interrupt) rx fifo trigger level rx fifo trigger level 8 12 rtscts1
XR16V2652 17 rev. 1.0.2 high performance duart with 32-byte fifo 2.16 auto xon/xoff (software) flow control when software flow control is enabled ( see table 14 ), the v2652 compares one or two sequential receive data characters with the programmed xon or xoff-1,2 character value(s). if receive character(s) (rx) match the programmed values, the v2652 will halt transmission (tx) as soon as t he current character has completed transmission. when a match occurs, the xoff (if enabled vi a ier bit-5) flag will be set and the interrupt output pin will be activated. followi ng a suspension due to a match of the xoff character, the v2652 will monitor the receive data stream for a match to t he xon-1,2 character. if a match is found, the v2652 will resume operation and clear the flags (isr bit-4). reset initially sets the contents of the xon/xoff 8-bit fl ow control registers to 0x00. following reset the user can write any xon/xoff value desired for software flow cont rol. different conditions can be set to detect xon/xoff characters ( see table 14 ) and suspend/resume transmissions. when double 8-bit xon/xoff characters are selected, the v2652 compares two cons ecutive receive characters with two so ftware flow control 8-bit values (xon1, xon2, xoff1, xoff2) and controls tx transmissi ons accordingly. under the above described flow control mechanisms, flow control characters are not placed (sta cked) in the user accessible rx data buffer or fifo. in the event that the receive buffer is overfilling and flow control needs to be executed, the v2 652 automatically sends an xoff message via the serial tx output to the remote modem. the v2652 sends the xoff-1,2 characters two-character times (= time taken to send two characters at the programmed baud rate) after the receive fifo crosses the selected tr igger level. to clear this conditio n, the v2652 will trans mit the programmed xon-1,2 characters as soon as receive fifo is less th an one trigger level below t he selected trigger level. table 7 below explains this. * after the trigger level is reached, an xoff character is se nt after a short span of time (= time required to send 2 characters); for example, after 2.083ms has elapsed for 9600 baud and 10-bit word length setting. 2.17 special character detect a special character detect feature is provided to detect an 8-bit character when bit-5 is set in the enhanced feature register (efr). when this character (xoff2) is detected, it will be placed in the fi fo along with normal incoming rx data. the v2652 compares each incoming re ceive character with xoff-2 data. if a match exists, the received data will be transferred to fifo and isr bit-4 will be set to indica te detection of special character. although the internal register table shows xon, xoff registers with eight bits of character information, the actual number of bits is dependent on the programmed word lengt h. line control register (lcr) bits 0-1 defines the number of character bits, i.e., either 5 bits, 6 bits, 7 bits, or 8 bits. the word length selected by lcr bits 0-1 also determines the number of bits that will be used for the special character comparison. bit-0 in the xon, xoff registers corresponds with the lsb bit for the receive character. t able 7: a uto x on /x off (s oftware ) f low c ontrol rx t rigger l evel int p in a ctivation x off c haracter ( s ) s ent ( characters in rx fifo ) x on c haracter ( s ) s ent ( characters in rx fifo ) 8 8 8* 0 16 16 16* 8 24 24 24* 16 28 28 28* 24
XR16V2652 18 high performance duart with 32-byte fifo rev. 1.0.2 2.18 infrared mode the v2652 uart includes the infrared encoder and decoder compatible to the irda (infrared data association) version 1.0. the irda 1.0 standard th at stipulates the infrared encoder sends out a 3/16 of a bit wide high-pulse for each ?0? bit in the transmit data st ream. this signal encoding reduces the on-time of the infrared led, hence reduces the power consumption. see figure 11 below. the infrared encoder and decoder are enabled by setting m cr register bit-6 to a ?1?. when the infrared feature is enabled, the transmit data output, tx, idles at logic zero level. likewise, the rx input assumes an idle level of logic zero from a reset and power up, see figure 11 . typically, the wireless infrared decoder receives the input pulse from the infrared sensing diode on the rx pin. each time it senses a light pulse, it returns a logic 1 to the data bit stream. however, this is not true with some infrared modules on the market which indicate a logic 0 by a light pulse. so the v2652 has a provision to invert the input polarity to accommodate this . in this case user can enable mcr bit-2 to invert the input signal. f igure 11. i nfrared t ransmit d ata e ncoding and r eceive d ata d ecoding character data bits start stop 0000 0 11 111 bit time 1/16 clock delay irdecoder-1 rx data receive ir pulse (rx pin) character data bits start stop 0000 0 11 111 tx data transmit ir pulse (tx pin) bit time 1/2 bit time 3/16 bit time irencoder-1
XR16V2652 19 rev. 1.0.2 high performance duart with 32-byte fifo 2.19 sleep mode with auto wake-up the v2652 supports low voltage system designs, hence, a sleep mode is included to reduce its power consumption when the chip is not actively used. all of these conditions must be satisf ied for the v2652 to enter sleep mode: no interrupts pending for both channels of the v2652 (isr bit-0 = 1) sleep mode of both channels are enabled (ier bit-4 = 1) modem inputs are not toggling (msr bits 0-3 = 0) rx input pins are idling high the v2652 stops its crystal oscillator to conserve power in th e sleep mode. user can check the xtal2 pin for no clock output as an indication that the device has entered the sleep mode. the v2652 resumes normal operation by any of the following: a receive data start bit transition (high to low) a data byte is loaded to the transmitter, thr or fifo a change of logic state on any of the modem or general purpose serial inputs: cts#, dsr#, cd#, ri# if the v2652 is awakened by any one of the above conditions, it will return to the sleep mode aut omatically after all interrupting conditions have been serviced and cleared. if the v2652 is awakened by the modem inputs, a read to the msr is required to re set the modem inputs. in any case, t he sleep mode will not be entered while an interrupt is pending from channel a or b. the v2652 will stay in the sleep mode of operation until it is disabled by setting ier bit-4 to a logic 0. if the address lines, data bus lines, iow#, ior#, cs#, chs el, and modem input lines remain steady when the v2652 is in sleep mode, the maximum current will be in the microamp range as specified in the dc electrical characteristics on page 37 . if the input lines are floating or are toggling while the v2652 is in sleep mode, the current can be up to 100 times more. if any of those signals are toggling or floating, then an external buffer would be required to keep the address, data and control lines steady to achieve the low current. as an alternative, please refer to the xr16v2651 which is pin-to-pin and software compatible with the v2652 but with some additional pins and the powersave feature that eliminates any unnecessary external buffer. a word of caution: owing to the star ting up delay of the crystal oscillato r after waking up from sleep mode, the first few receive characters may be lost. the number of ch aracters lost during the restart also depends on your operating data rate. more characters are lost when operati ng at higher data rate. also, it is important to keep rx a/b inputs idling high or ?mar king? condition during sleep mode to avoid receiving a ?break? condition upon the restart. this may occur when the external inte rface transceivers (rs-232, rs-422 or another type) are also put to sleep mode and cannot maintain the ?mar king? condition. to avoid this, the designer can use a 47k-100k ohm pull-up resistor on the rxa and rxb pins.
XR16V2652 20 high performance duart with 32-byte fifo rev. 1.0.2 2.20 internal loopback the v2652 uart provides an inter nal loopback capability for system diagnostic purposes. the internal loopback mode is enabled by setting mcr register bit-4 to logi c 1. all regular uart functions operate normally. figure 12 shows how the modem port signals are re-configured. transmit data from the transmit shift register output is internally routed to the receive shift register input allowing the system to re ceive the same data that it was sending. the tx, rts# and dtr# pins are held while the cts#, dsr# cd# and ri# inputs are ignored. caution: the rx input pin must be held high during loopback test else upon exiting the loopback test the uart may detect and report a false ?break? signal. also , auto rts/cts flow control is not supported during internal loopback. f igure 12. i nfrared t ransmit d ata e ncoding and r eceive d ata d ecoding txa/txb rxa/rxb modem / general purpose control logic internal data bus lines and control signals rtsa#/rtsb# mcr bit-4=1 vcc vcc transmit shift register (thr/fifo) receive shift register (rhr/fifo) ctsa#/ctsb# dtra#/dtrb# dsra#/dsrb# ria#/rib# cda#/cdb# op1# op2# rts# cts# dtr# dsr# ri# cd# vcc vcc op2a#/op2b#
XR16V2652 21 rev. 1.0.2 high performance duart with 32-byte fifo 3.0 uart internal registers each of the uart channel in the v2652 has its own set of configuration registers selected by address lines a0, a1 and a2 with cs# or chsel selecting the ch annel. the complete register set is shown on table 8 and table 9 . t able 8: uart channel a and b uart internal registers a ddresses a2 a1 a0 r egister r ead /w rite c omments 16c550 c ompatible r egisters 0 0 0 rhr - receive holding register thr - transmit holding register read-only write-only lcr[7] = 0 0 0 0 dll - divisor lsb read/write lcr[7] = 1, lcr 0xbf 0 0 1 dlm - divisor msb read/write 0 1 0 afr - alternate function register read/write lcr[7] = 1, lcr 0xbf, efr[4] = 0 0 1 0 dld - divisor fractional read/write lcr[7] = 1, lcr 0xbf, efr[4] = 1 0 0 0 drev - device revision code read-only dll, dlm = 0x00, lcr[7] = 1, lcr 0xbf 0 0 1 dvid - device identification code read-only 0 0 1 ier - interrupt enable register read/write lcr[7] = 0 0 1 0 isr - interrupt status register fcr - fifo control register read-only write-only 0 1 1 lcr - line control register read/write 1 0 0 mcr - modem control register read/write lcr 0xbf 1 0 1 lsr - line status register read-only 1 1 0 msr - modem status register read-only 1 1 1 spr - scratch pad register read/write e nhanced r egisters 0 1 0 efr - enhanced function register read/write lcr = 0xbf 1 0 0 xon-1 - xon character 1 read/write 1 0 1 xon-2 - xon character 2 read/write 1 1 0 xoff-1 - xoff character 1 read/write 1 1 1 xoff-2 - xoff character 2 read/write
XR16V2652 22 high performance duart with 32-byte fifo rev. 1.0.2 . t able 9: internal registers description. s haded bits are enabled when efr b it -4=1 a ddress a2-a0 r eg n ame r ead / w rite b it -7 b it -6 b it -5 b it -4 b it -3 b it -2 b it -1 b it -0 c omment 16c550 compatible registers 0 0 0 rhr rd bit-7 bit-6 bit-5 bit-4 bit-3 bit-2 bit-1 bit-0 lcr[7]=0 0 0 0 thr wr bit-7 bit-6 bit-5 bit-4 bit-3 bit-2 bit-1 bit-0 0 0 1 ier rd/wr 0/ 0/ 0/ 0/ modem stat. int. enable rx line stat. int. enable tx empty int enable rx data int. enable cts int. enable rts int. enable xoff int. enable sleep mode enable 0 1 0 isr rd fifos enabled fifos enabled 0/ 0/ int source bit-3 int source bit-2 int source bit-1 int source bit-0 int source bit-5 int source bit-4 0 1 0 fcr wr rx fifo trigger rx fifo trigger 0/ 0/ dma mode enable tx fifo reset rx fifo reset fifos enable tx fifo trigger tx fifo trigger 0 1 1 lcr rd/wr divisor enable set tx break set parity even parity parity enable stop bits word length bit-1 word length bit-0 1 0 0 mcr rd/wr 0/ 0/ 0/ internal lopback enable op2# output control op1# rts# output control dtr# output control lcr 0xbf brg pres - caler ir mode enable xonany ir invert 1 0 1 lsr rd rx fifo global error thr & tsr empty thr empty rx break rx framing error rx parity error rx over - run error rx data ready 1 1 0 msr rd cd# input ri# input dsr# input cts# input delta cd# delta ri# delta dsr# delta cts# 1 1 1 spr rd/wr bit-7 bit-6 bit-5 bit-4 bit-3 bit-2 bit-1 bit-0 lcr 0xbf baud rate generator divisor 0 0 0 dll rd/wr bit-7 bit-6 bit-5 bit-4 bit-3 bit-2 bit-1 bit-0 lcr[7]=1 lcr 0xbf 0 0 1 dlm rd/wr bit-7 bit-6 bit-5 bit-4 bit-3 bit-2 bit-1 bit-0 0 1 0 afr rd/wr rsvd rsvd rsvd rsvd rsvd rxrdy# select baudout# select concur - rent write lcr[7]=1 lcr 0xbf efr[4] = 0 0 1 0 dld rd/wr 0 0 4x mode 8x mode bit-3 bit-2 bit-1 bit-0 lcr[7]=1 lcr 0xbf efr[4] = 1
XR16V2652 23 rev. 1.0.2 high performance duart with 32-byte fifo 4.0 internal register descriptions 4.1 receive holding register (rhr) - read- only see?receiver? on page 13. 4.2 transmit holding register (thr) - write-only see?transmitter? on page 12. 4.3 interrupt enable register (ier) - read/write the interrupt enable register (ier) masks the interrupts from receive data ready, transmit empty, line status and modem status registers. these interrupts are r eported in the interrupt status register (isr). 4.3.1 ier versus receive fifo interrupt mode operation when the receive fifo (fcr bit-0 = 1) and receive interr upts (ier bit-0 = 1) are enabled, the rhr interrupts (see isr bits 2 and 3) status will reflect the following: a. the receive data available interrupts are issued to the host when the fifo has reached the programmed trigger level. it will be cleared when the fifo drops below the programmed trigger level. b. fifo level will be reflected in the isr register when the fifo trigger level is reached. both the isr register status bit and the interrupt will be cleared wh en the fifo drops below the trigger level. c. the receive data ready bit (lsr bit-0) is set as soon as a character is transferred from the shift register to the receive fifo. it is rese t when the fifo is empty. 0 0 0 drev rd bit-7 bit-6 bit-5 bit-4 bit-3 bit-2 bit-1 bit-0 lcr[7]=1 lcr 0xbf dll=0x00 dlm=0x00 0 0 1 dvid rd 0 0 0 0 0 1 1 0 enhanced registers 0 1 0 efr rd/wr auto cts enable auto rts enable special char select enable ier [7:4], isr [5:4], fcr[5:4], mcr[7:5], dld soft- ware flow cntl bit-3 soft - ware flow cntl bit-2 soft - ware flow cntl bit-1 soft - ware flow cntl bit-0 lcr=0 x bf 1 0 0 xon1 rd/wr bit-7 bit-6 bit-5 bit-4 bit-3 bit-2 bit-1 bit-0 1 0 1 xon2 rd/wr bit-7 bit-6 bit-5 bit-4 bit-3 bit-2 bit-1 bit-0 1 1 0 xoff1 rd/wr bit-7 bit-6 bit-5 bit-4 bit-3 bit-2 bit-1 bit-0 1 1 1 xoff2 rd/wr bit-7 bit-6 bit-5 bit-4 bit-3 bit-2 bit-1 bit-0 t able 9: internal registers description. s haded bits are enabled when efr b it -4=1 a ddress a2-a0 r eg n ame r ead / w rite b it -7 b it -6 b it -5 b it -4 b it -3 b it -2 b it -1 b it -0 c omment
XR16V2652 24 high performance duart with 32-byte fifo rev. 1.0.2 4.3.2 ier versus receive/transmit fifo polled mode operation when fcr bit-0 equals a logic 1 for fifo enable; resett ing ier bits 0-3 enables the XR16V2652 in the fifo polled mode of operation. since the receiver and transmitter have separate bits in the lsr either or both can be used in the polled mode by selecting respective transmit or receive control bit(s). a. lsr bit-0 indicates there is data in rhr or rx fifo. b. lsr bit-1 indicates an overrun error has occurred and that data in the fifo may not be valid. c. lsr bit 2-4 provides the type of receive data erro rs encountered for the data byte in rhr, if any. d. lsr bit-5 indicates thr is empty. e. lsr bit-6 indicates when both the transmit fifo and tsr are empty. f. lsr bit-7 indicates a data error in at least one character in the rx fifo. ier[0]: rhr interrupt enable the receive data ready interrupt will be issued when rhr has a data character in th e non-fifo mode or when the receive fifo has reached the programmed trigger level in the fifo mode. ? logic 0 = disable the receive data ready interrupt (default). ? logic 1 = enable the receiver data ready interrupt. ier[1]: thr interrupt enable this bit enables the transmit ready interrupt which is issued whenever the thr becomes empty in the non- fifo mode or when data in the fifo fa lls below the programmed trigger level in the fifo mode. if the thr is empty when this bit is enabled , an interrupt will be generated. ? logic 0 = disable transmit ready interrupt (default). ? logic 1 = enable transmit ready interrupt. ier[2]: receive line status interrupt enable if any of the lsr register bits 1, 2, 3 or 4 is a logic 1, it will generate an interrupt to inform the host controller about the error status of the current data byte in fi fo. lsr bit-1 generates an interrupt immediately when the character has been received. lsr bits 2-4 generate an in terrupt when the character with errors is read out of the fifo (default). ? logic 0 = disable the receiver line status interrupt (default). ? logic 1 = enable the receiver line status interrupt. ier[3]: modem status interrupt enable ? logic 0 = disable the modem status register interrupt (default). ? logic 1 = enable the modem status register interrupt. ier[4]: sleep mode enable (requires efr bit-4 = 1) ? logic 0 = disable sleep mode (default). ? logic 1 = enable sleep mode. see sleep mode section for further details. ier[5]: xoff interrupt enable (requires efr bit-4=1) ? logic 0 = disable the software flow cont rol, receive xoff interrupt (default). ? logic 1 = enable the software flow control, receive xo ff interrupt. see software flow control section for details. ier[6]: rts# output interrupt enable (requires efr bit-4=1) ? logic 0 = disable the rts# interrupt (default).
XR16V2652 25 rev. 1.0.2 high performance duart with 32-byte fifo ? logic 1 = enable the rts# interrupt. the uart issues an interrupt when the rts# pin makes a transition from low to high. ier[7]: cts# input interrupt enable (requires efr bit-4=1) ? logic 0 = disable the cts# interrupt (default). ? logic 1 = enable the cts# interrupt. the uart issues an interrupt when cts# pin makes a transition from low to high. 4.4 interrupt status register (isr) - read-only the uart provides multiple levels of prioritized interrupts to minimize external software interaction. the interrupt status register (isr) provides the user with six interrupt status bits. performing a read cycle on the isr will give the user the current hi ghest pending interrupt level to be se rviced, others are queued up to be serviced next. no other interrupts are acknowledged until the pending interrupt is serviced. the interrupt source table, table 10 , shows the data values (bit 0-5) for the inte rrupt priority levels an d the interr upt sources associated with each of these interrupt levels. 4.4.1 interrupt generation: ? lsr is by any of the lsr bits 1, 2, 3 and 4. ? rxrdy is by rx trigger level. ? rxrdy time-out is by a 4-char plus 12 bits delay timer. ? txrdy is by tx trigger level or tx fifo empty. ? msr is by any of the msr bits 0, 1, 2 and 3. ? receive xoff/special character is by det ection of a xoff or special character. ? cts# is when its transmitter toggles the input pin (f rom low to high) during auto cts flow control. ? rts# is when its receiver toggles the output pin (f rom low to high) during auto rts flow control. 4.4.2 interrupt clearing: ? lsr interrupt is cleared by a read to the lsr register. ? rxrdy interrupt is cleared by reading data until fifo fa lls below the trigger level. ? rxrdy time-out interrupt is cleared by reading rhr. ? txrdy interrupt is cleared by a read to the isr register or writing to thr. ? msr interrupt is cleared by a read to the msr register. ? xoff interrupt is cleared by a read to isr or when xon character(s) is received. ? special character interrupt is cleared by a read to isr or after the next character is received. ? rts# and cts# flow control interrupts are cleared by a read to the msr register.
XR16V2652 26 high performance duart with 32-byte fifo rev. 1.0.2 ] isr[0]: interrupt status ? logic 0 = an interrupt is pending and the isr contents may be used as a pointer to the appropriate interrupt service routine. ? logic 1 = no interrupt pending (default condition). isr[3:1]: interrupt status these bits indicate the source for a pending interrupt at interrupt priority levels (see interrupt source table 10 ). isr[4]: xoff/xon or special character interrupt status this bit is enabled when efr bit-4 is set to a logic 1. is r bit-4 indicates that the receiver detected a data match of the xoff character(s). if this is an xoff/xon interrupt, it can be cleared by a read to the isr. if it is a special character interr upt, it can be cleared by reading isr or it will automatically clear after the next character is received. isr[5]: rts#/cts# interrupt status this bit is enabled when efr bit-4 is set to a logic 1. isr bit-5 indicates that the cts# or rts# has been de- asserted. isr[7:6]: fifo enable status these bits are set to a logic 0 when the fifos are disa bled. they are set to a logic 1 when the fifos are enabled. 4.5 fifo control register (fcr) - write-only this register is used to enable the fifos, clear the fi fos, set the transmit/receive fifo trigger levels, and select the dma mode. the dma, and fifo modes are defined as follows: fcr[0]: tx and rx fifo enable ? logic 0 = disable the transmit and receive fifo (default). ? logic 1 = enable the transmit and receive fifos. this bit must be set to logic 1 when other fcr bits are written or they will not be programmed. t able 10: i nterrupt s ource and p riority l evel p riority isr r egister s tatus b its s ource of interrupt l evel b it -5 b it -4 b it -3 b it -2 b it -1 b it -0 1 0 0 0 1 1 0 lsr (receiver line status register) 2 0 0 1 1 0 0 rxrdy (receive data time-out) 3 0 0 0 1 0 0 rxrdy (received data ready) 4 0 0 0 0 1 0 txrdy (transmit ready) 5 0 0 0 0 0 0 msr (modem status register) 6 0 1 0 0 0 0 rxrdy (received xoff or special character) 7 1 0 0 0 0 0 cts#, rts# change of state - 0 0 0 0 0 1 none (default)
XR16V2652 27 rev. 1.0.2 high performance duart with 32-byte fifo fcr[1]: rx fifo reset this bit is only active when fcr bit-0 is a ?1?. ? logic 0 = no receive fifo reset (default) ? logic 1 = reset the receive fifo pointers and fifo le vel counter logic (the rece ive shift register is not cleared or altered). this bit will return to a logic 0 after resetting the fifo. fcr[2]: tx fifo reset this bit is only active when fcr bit-0 is a ?1?. ? logic 0 = no transmit fifo reset (default). ? logic 1 = reset the transmit fifo pointers (the transmit shift register is not clear ed or altered). this bit will return to a logic 0 after resetting the fifo. fcr[3]: dma mode select controls the behavior of the txrdy# and rxrdy# pins. see dma operation section for details. ? logic 0 = normal operation (default). ? logic 1 = dma mode. fcr[5:4]: transmit fifo trigger select (requires efr bit-4=1) (logic 0 = default, tx trigger level = 1) these 2 bits set the trigger level for the transmit fifo. the uart will issue a transmit interrupt when the number of characters in the fifo falls below the selected trigger level, or when it gets empty in case that the fifo did not get filled over the trigger level on last re-load. table 11 below shows the selections. efr bit-4 must be set to ?1? before these bits can be accessed. fcr[7:6]: receive fifo trigger select (logic 0 = default, rx trigger level =1) these 2 bits are used to se t the trigger level for the receive fifo. th e uart will issue a rece ive interrupt when the number of the characters in the fifo crosses the trigger level. table 11 shows the complete selections. 4.6 line control register (lcr) - read/write the line control register is used to specify the asynchronous data communication format. the word or character length, the number of stop bits, and the parity are selected by writing the appropriate bits in this register. t able 11: t ransmit and r eceive fifo t rigger t able and l evel s election fcr b it -7 fcr b it -6 fcr b it -5 fcr b it -4 r eceive t rigger l evel t ransmit t rigger l evel c ompatibility 0 0 1 1 0 1 0 1 0 0 1 1 0 1 0 1 8 16 24 28 16 8 24 30 16c650a
XR16V2652 28 high performance duart with 32-byte fifo rev. 1.0.2 lcr[1:0]: tx and rx word length select these two bits specify the word length to be transmitted or received. lcr[2]: tx and rx stop-bit length select the length of stop bit is specified by this bi t in conjunction with the programmed word length. lcr[3]: tx and rx parity select parity or no parity can be selected via this bit. the pa rity bit is a simple way used in communications for data integrity check. see table 12 for parity selection summary below. ? logic 0 = no parity. ? logic 1 = a parity bit is generated during the transmissi on while the receiver checks for parity error of the data character received. lcr[4]: tx and rx parity select if the parity bit is enabled with lcr bit-3 set to a logic 1, lcr bit-4 selects the even or odd parity format. ? logic 0 = odd parity is generated by forcing an odd number of logic 1?s in the transmitted character. the receiver must be programmed to check the same format (default). ? logic 1 = even parity is gen erated by forcing an even numb er of logic 1?s in the tr ansmitted character. the receiver must be programmed to check the same format. lcr[5]: tx and rx parity select if the parity bit is enabled, lcr bit- 5 selects the forced parity format. ? lcr bit-5 = logic 0, parity is not forced (default). ? lcr bit-5 = logic 1 and lcr bit-4 = logic 0, parity bi t is forced high for the transmit and receive data. ? lcr bit-5 = logic 1 and lcr bit-4 = logic 1, parity bit is forced low for the transmit and receive data. bit-1 bit-0 w ord length 0 0 5 (default) 0 1 6 1 0 7 1 1 8 bit-2 w ord length s top bit length (b it time ( s )) 0 5,6,7,8 1 (default) 1 5 1-1/2 1 6,7,8 2
XR16V2652 29 rev. 1.0.2 high performance duart with 32-byte fifo lcr[6]: transmit break enable when enabled, the break control bit causes a break cond ition to be transmitted (the tx output is forced to a ?space", low state). this condition remains, unt il disabled by setting lcr bit-6 to a logic 0. ? logic 0 = no tx break condition (default). ? logic 1 = forces the transmitter output (tx) to a ?space?, low, for alerting the remote receiver of a line break condition. lcr[7]: baud rate divisors enable baud rate generator divisor (dll, dlm and dld) enable. ? logic 0 = data registers are selected (default). ? logic 1 = divisor latch registers are selected. 4.7 modem control register (mcr) or general purpose outputs control - read/write the mcr register is used for controlling the serial/mod em interface signals or g eneral purpose inputs/outputs. mcr[0]: dtr# output the dtr# pin is a modem control outpu t. if the modem interface is not us ed, this output may be used as a general purpose output. ? logic 0 = force dtr# output high (default). ? logic 1 = force dtr# output low. mcr[1]: rts# output the rts# pin is a modem control output and may be used for automatic hardware flow control by enabled by efr bit-6. if the modem interface is not used, this output may be used as a general purpose output. ? logic 0 = force rts# high (default). ? logic 1 = force rts# low. mcr[2]: irda rx inversion or op1# (legacy term) when infrared mode is enabled (mcr[6]=1 and efr[4]=1), this bit selects the idle state of the encoded irda data. in internal loopback mode, this bi t functions like the op 1# in the 16c550. ? logic 0 = select rx input as ac tive-low encoded irda data (i dle state will be low) (default). ? logic 1 = select rx input as active-high encoded irda data (idle state will be high). in the internal loopback mode , this bit controls the state of the mode m input ri# bit in the msr register as shown in figure 12 . t able 12: p arity selection lcr b it -5 lcr b it -4 lcr b it -3 p arity selection x x 0 no parity 0 0 1 odd parity 0 1 1 even parity 1 0 1 force parity to mark, high 1 1 1 force parity to space, low
XR16V2652 30 high performance duart with 32-byte fifo rev. 1.0.2 mcr[3]: op2# output if op2# is selected as the mf# output, then this bit controls the state of this general purpose output. ? logic 0 = op2# output set high(default). ? logic 1 = op2# output set low. mcr[4]: internal loopback enable ? logic 0 = disable loopback mode (default). ? logic 1 = enable local loopback mode, see loopback section and figure 12 . mcr[5]: xon-any enable (requires efr bit-4=1) ? logic 0 = disable xon-any function (default). ? logic 1 = enable xon-any function. in this mode, any rx character re ceived will resume transmit operation. the rx character will be loaded into the rx fifo, unless the rx characte r is an xon or xo ff character and the v2652 is programmed to use the xon/xoff flow control. mcr[6]: infrared encoder/decoder enable (requires efr bit-4=1) ? logic 0 = enable the standard modem receive an d transmit input/output interface (default). ? logic 1 = enable infrared irda receive and transmit inputs/outputs. the tx/rx output/input are routed to the infrared encoder/decoder. the data input and output levels conform to the irda infrared interface requirement. while in this mode, the infrared tx ou tput will be idling low. see?infrared mode? on page 18. mcr[7]: clock prescaler select (requires efr bit-4=1) ? logic 0 = divide by one. the input clock from the crystal or external clock is fed directly to the programmable baud rate generator without further modification, i.e., divide by one (default). ? logic 1 = divide by four. the prescaler divides the input clock from the crystal or external clock by four and feeds it to the programmable baud rate generator, hence, data rates become one forth. 4.8 line status register (lsr) - read only this register provides the status of data transfers between the uart and the host. lsr[0]: receive data ready indicator ? logic 0 = no data in receive holding register or fifo (default). ? logic 1 = data has been received and is save d in the receive holding register or fifo. lsr[1]: receiver overrun error flag ? logic 0 = no overrun error (default). ? logic 1 = overrun error. a data overrun error condition occurred in the receive shift register. this happens when additional data arrives while the fi fo is full. in this case the previous data in the receive shift register is overwritten. note that under this condition the data byte in the receive shift register is not transferred into the fifo, therefore the data in the fifo is not corrupted by the error. lsr[2]: receive data parity error tag ? logic 0 = no parity error (default). ? logic 1 = parity error. the receive character in rhr does not have correct pa rity information and is suspect. this error is associated with the char acter available for reading in rhr.
XR16V2652 31 rev. 1.0.2 high performance duart with 32-byte fifo lsr[3]: receive data framing error tag ? logic 0 = no framing error (default). ? logic 1 = framing error. the receive character did not hav e a valid stop bit(s). this error is associated with the character available for reading in rhr. lsr[4]: receive break error tag ? logic 0 = no break condition (default). ? logic 1 = the receiver received a break signal (rx wa s low for at least one char acter frame time). in the fifo mode, only one break character is loaded into the fifo. lsr[5]: transmit holding register empty flag this bit is the transmit holding register empty indicator. the thr bit is set to a logic 1 when the last data byte is transferred from the transmit holding register to th e transmit shift register. t he bit is reset to logic 0 concurrently with the data loading to the transmit holding r egister by the host. in the fifo mode this bit is set when the transmit fifo is empty, it is cleared when the transmit fifo contains at least 1 byte. lsr[6]: thr and tsr empty flag this bit is set to a logic 1 whenever the transmitter goes idle. it is set to logic 0 whenever either the thr or tsr contains a data character. in the fifo mode this bi t is set to a logic 1 whenever the transmit fifo and transmit shift register are both empty. lsr[7]: receive fifo data error flag ? logic 0 = no fifo error (default). ? logic 1 = a global indicator for the sum of all error bits in the rx fifo. at least one parity error, framing error or break indication is in the fifo data. this bit clears wh en there is no more error(s) in any of the bytes in the rx fifo. 4.9 modem status register (msr) - read only this register provides the current state of the modem interf ace input signals. lower four bits of this register are used to indicate the changed information. these bits are set to a logic 1 whenever a signal from the modem changes state. these bits may be used for general purpose inputs when they are not used with modem signals. msr[0]: delta cts# input flag ? logic 0 = no change on cts# input (default). ? logic 1 = the cts# input has changed state since the la st time it was monitored. a modem status interrupt will be generated if msr interrup t is enabled (ier bit-3). msr[1]: delta dsr# input flag ? logic 0 = no change on dsr# input (default). ? logic 1 = the dsr# input has changed state since the last time it was monitored. a modem status interrupt will be generated if msr interrup t is enabled (ier bit-3). msr[2]: delta ri# input flag ? logic 0 = no change on ri# input (default). ? logic 1 = the ri# input has changed from a low to high, ending of the ringing signal. a modem status interrupt will be ge nerated if msr in terrupt is enabled (ier bit-3).
XR16V2652 32 high performance duart with 32-byte fifo rev. 1.0.2 msr[3]: delta cd# input flag ? logic 0 = no change on cd# input (default). ? logic 1 = indicates that the cd# input has changed st ate since the last time it was monitored. a modem status interrupt will be generated if ms r interrupt is enab led (ier bit-3). msr[4]: cts input status cts# pin may function as automatic hardware flow control signal input if it is enabled and selected by auto cts (efr bit-7). auto cts flow control allows starting and stopping of local data transmissions based on the modem cts# signal. a high on the cts# pin will stop uart transmitte r as soon as the current character has finished transmission, and a low will re sume data transmission. normally ms r bit-4 bit is the complement of the cts# input. however in the loopback mode, this bit is equivalent to the rts# bit in the mcr register. the cts# input may be used as a general purpose input when the modem interface is not used. msr[5]: dsr input status normally this bit is the complement of the dsr# input. in the loopback mode , this bit is equivalent to the dtr# bit in the mcr register. the dsr# input may be used as a general purpose input when the modem interface is not used. msr[6]: ri input status normally this bit is the complement of the ri# input. in the loopback mode th is bit is equivalent to bit-2 in the mcr register. the ri# input may be used as a general purpose input when the modem interface is not used. msr[7]: cd input status normally this bit is the complement of the cd# input. in the loopback mode this bit is equivalent to bit-3 in the mcr register. the cd# input may be used as a general purpose input when the modem interface is not used. 4.10 scratch pad register (spr) - read/write this is a 8-bit general purpose register for the user to store temporary data. the co ntent of this register is preserved during sleep mode but becomes 0xff (default) after a reset or a power off-on cycle. 4.11 baud rate generator registers (dll, dlm and dld) - read/write these registers make-up the value of the baud rate divi sor. the concatenation of the contents of dlm and dll is a 16-bit value is then added to dld[3:0]/16 to achieve the fractional baud rate divisor. dld must be enabled via efr bit-4 before it can be accessed. see?programmable baud rate generator with fractional divisor? on page 10. dld[5:4]: sampli ng rate select these bits select the data sampling rate. by default, the data sampling rate is 16x. the maximum data rate will double if the 8x mode is sele cted and will quadruple if the 4x mo de is selected. see table below. dld[7:6]: reserved 4.12 alternate function register (afr) - read/write this register is used to select spec ific modes of mf# operation and to allow both uart register sets to be written concurrently. t able 13: s ampling r ate s elect dld[5] dld[4] s ampling r ate 0 0 16x 0 1 8x 1 x 4x
XR16V2652 33 rev. 1.0.2 high performance duart with 32-byte fifo afr[0]: concurrent write mode when this bit is set, the cpu can wr ite concurrently to the sa me register in both ua rts. this function is intended to reduce the dual uart initialization time . it can be used by the cpu when both channels are initialized to the same state. the external cpu can set or clear this bit by accessing either register set. when this bit is set, the channel select pi n still selects the channel to be access ed during read oper ations. the user should ensure that lcr bit-7 of both channels are in t he same state before executing a concurrent write to the registers at address 0, 1, or 2. ? logic 0 = no concurrent write (default). ? logic 1 = register set a and b are written concurrent ly with a single external cpu i/o write operation. afr[2:1]: mf# output select these bits select a signal function for output on th e mf# a/b pins. these signal function are described as: op2#, baudout#, or rxrdy#. only one sign al function can be selected at a time. afr[7:3]: reserved all are initialized to logic 0. 4.13 device identification register (dvid) - read only this register contains the device id (0x06 for xr16v2 652). prior to reading this register, dll and dlm should be set to 0x00 (dld = 0xxx). 4.14 device revision register (drev) - read only this register contains the device revision information. for example, 0x01 means revision a. prior to reading this register, dll and dlm should be set to 0x00 (dld = 0xxx). 4.15 enhanced feature register (efr) enhanced features are enabled or disabled using this register. bit 0-3 provide si ngle or dual consecutive character software flow control selection (see table 14 ). when the xon1 and xon2 and xoff1 and xoff2 modes are selected, the double 8-bit words are concatenated in to two sequential characters. caution: note that whenever changing the tx or rx flow control bits, always reset all bits back to logic 0 (disable) before programming a new setting. b it -2 b it -1 mf# f unction 0 0 op2# (default) 0 1 baudout# 1 0 rxrdy# 1 1 reserved
XR16V2652 34 high performance duart with 32-byte fifo rev. 1.0.2 efr[3:0]: software flow control select single character and dual sequential characters software flow control is supported. combinations of software flow control can be selected by programming these bits. efr[4]: enhanced function bits enable enhanced function control bit. this bit enables ier bits 4- 7, isr bits 4-5, fcr bits 4-5, mcr bits 5-7, and dld to be modified. after modifying any enhanced bits, efr bit-4 can be set to a logic 0 to latch the new values. this feature prevents legacy software from altering or overwriting the enhanced functions once set. normally, it is recommended to leave it enabled, logic 1. ? logic 0 = modification disable/latch enhanced features. ie r bits 4-7, isr bits 4-5, fcr bits 4-5, mcr bits 5- 7, and dld are saved to retain the user settings. after a reset, the ier bits 4-7, is r bits 4-5, fcr bits 4-5, mcr bits 5-7, and dld are set to a logic 0 to be compatible with st16c550 mode (default). ? logic 1 = enables the above-mentioned regist er bits to be modified by the user. efr[5]: special character detect enable ? logic 0 = special character detect disabled (default). ? logic 1 = special character detect enabled. the ua rt compares each incoming receive character with data in xoff-2 register. if a match exists, the receive data will be transfer red to fifo and isr bit-4 will be set to indicate detection of the special character. bit-0 co rresponds with the lsb bit of the receive character. if flow control is set for comparing xon1, xo ff1 (efr [1:0]= ?10?) then flow control and special character work normally. however, if flow control is set for comparing xon2, xoff2 (efr[1:0]= ?01?) then flow control works normally, but xoff2 will not go to the fifo, and will g enerate an xoff interrupt and a special character interrupt, if enabled via ier bit-5. t able 14: s oftware f low c ontrol f unctions efr bit -3 c ont -3 efr bit -2 c ont -2 efr bit -1 c ont -1 efr bit -0 c ont -0 t ransmit and r eceive s oftware f low c ontrol 0 0 0 0 no tx and rx flow control (default and reset) 0 0 x x no transmit flow control 1 0 x x transmit xon1, xoff1 0 1 x x transmit xon2, xoff2 1 1 x x transmit xon1 and xon2, xoff1 and xoff2 x x 0 0 no receive flow control x x 1 0 receiver compares xon1, xoff1 x x 0 1 receiver compares xon2, xoff2 1 0 1 1 transmit xon1, xoff1 receiver compares xon1 or xon2, xoff1 or xoff2 0 1 1 1 transmit xon2, xoff2 receiver compares xon1 or xon2, xoff1 or xoff2 1 1 1 1 transmit xon1 and xon2, xoff1 and xoff2, receiver compares xon1 and xon2, xoff1 and xoff2 0 0 1 1 no transmit flow control, receiver compares xon1 and xon2, xoff1 and xoff2
XR16V2652 35 rev. 1.0.2 high performance duart with 32-byte fifo efr[6]: auto rts flow control enable rts# output may be used for hardware flow control by setting efr bit-6 to logic 1. when auto rts is selected, an interrupt will be generated when the receive fifo is fi lled to the programm ed trigger level and rts de-asserts high at the next upper trigger level or hysteresis level. rts# will return low when fifo data falls below the next lower trigger le vel. the rts# output must be asserted (low) before the auto rts can take effect. rts# pin will function as a general purp ose output when ha rdware flow control is disabled. ? logic 0 = automatic rts flow control is disabled (default). ? logic 1 = enable automatic rts flow control. efr[7]: auto cts flow control enable automatic cts flow control. ? logic 0 = automatic cts flow control is disabled (default). ? logic 1 = enable automatic cts flow control. data transmission stops when cts# input de-asserts high. data transmission resumes when cts# returns low. 4.15.1 software flow control registers (xoff1, xoff2, xon1, xon2) - read/write these registers are used as the programmable software flow control characters xoff1, xoff2, xon1, and xon2. for more details, see table 7 .
XR16V2652 36 high performance duart with 32-byte fifo rev. 1.0.2 t able 15: uart reset conditions for channel a and b registers reset state dlm, dll dlm = 0x00 and dll = 0x01. only resets to these values during a power up. they do not reset when the reset pin is asserted. dld bits 7-0 = 0x00 afr bits 7-0 = 0x00 rhr bits 7-0 = 0xxx thr bits 7-0 = 0xxx ier bits 7-0 = 0x00 fcr bits 7-0 = 0x00 isr bits 7-0 = 0x01 lcr bits 7-0 = 0x00 mcr bits 7-0 = 0x00 lsr bits 7-0 = 0x60 msr bits 3-0 = logic 0 bits 7-4 = logic levels of the inputs inverted spr bits 7-0 = 0xff efr bits 7-0 = 0x00 xon1 bits 7-0 = 0x00 xon2 bits 7-0 = 0x00 xoff1 bits 7-0 = 0x00 xoff2 bits 7-0 = 0x00 i/o signals reset state tx high op2# high rts# high dtr# high rxrdy# high txrdy# low int low
XR16V2652 37 rev. 1.0.2 high performance duart with 32-byte fifo test 1: the following inputs must remain steady at vc c or gnd state to minimize sleep current: a0-a2, d0- d7, ior#, iow#, csa#, csb# and all modem inputs. also , rxa and rxb inputs must idle high while asleep. floating inputs will result in sleep cu rrents in the ma range. for powersave featur e that isolates address, data and control signals, please see the xr16v2651 datasheet. absolute maximum ratings power supply range 7 volts voltage at any pin gnd-0.3v to 7v operating temperature -40 o to +85 o c storage temperature -65 o to +150 o c package dissipation 500 mw typical package thermal resistance data ( margin of error: 15% ) thermal resistance (44-plcc) theta-ja = 50 o c/w, theta-jc = 21 o c/w thermal resistance (32-qfn) theta-ja = 33 o c/w, theta-jc = 22 o c/w electrical characteristics dc electrical characteristics ta=0 o to 70 o c (-40 o to +85 o c for industrial grade package ), v cc is 2.25v to 3.6v s ymbol p arameter l imits 2.5v m in m ax l imits 3.3v m in m ax u nits c onditions v ilck clock input low level -0.3 0.4 -0.3 0.6 v v ihck clock input high level 2.0 vcc 2.4 vcc v v il input low voltage -0.3 0.5 -0.3 0.7 v v ih input high voltage 1.8 5.5 2.0 5.5 v v ol output low voltage 0.4 0.4 v v i ol = 6 ma i ol = 4 ma v oh output high voltage 1.8 2.0 v v i oh = -4 ma i oh = -2 ma i il input low leakage current 10 10 ua i ih input high leakage current 10 10 ua c in input pin capacitance 5 5 pf i cc power supply current 1.5 2.5 ma ext clk = 2 mhz i sleep sleep current 15 30 ua see test 1
XR16V2652 38 high performance duart with 32-byte fifo rev. 1.0.2 ac electrical characteristics u nless otherwise noted : ta = -40 o to +85 o c, v cc =2.25 - 3.63v, 70 p f load where applicable s ymbol p arameter l imits 2.5v 10% m in m ax l imits 3.3v 10% m in m ax u nit xtal1 uart crystal oscillator 32 24 mhz eclk external clock 50 64 mhz t eclk external clock time period 10 7 ns t as address setup time 0 0 ns t ah address hold time 0 0 ns t cs chip select width 40 35 ns t rd ior# strobe width 40 35 ns t dy read cycle delay 40 35 ns t rdv data access time 35 30 ns t dd data disable time 25 25 ns t wr iow# strobe width 40 35 ns t dy write cycle delay 40 35 ns t ds data setup time 10 10 ns t dh data hold time 3 3 ns t wdo delay from iow# to output 50 50 ns t mod delay to set interrupt from modem input 50 50 ns t rsi delay to reset interrupt from ior# 50 50 ns t ssi delay from stop to set interrupt 1 1 bclk t rri delay from ior# to reset interrupt 45 45 ns t si delay from stop to interrupt 45 45 ns t int delay from initial int reset to transmit start 8 24 8 24 bclk t wri delay from iow# to reset interrupt 45 45 ns t ssr delay from stop to set rxrdy# 1 1 bclk t rr delay from ior# to reset rxrdy# 45 45 ns t wt delay from iow# to set txrdy# 45 45 ns t srt delay from center of start to reset txrdy# 8 8 bclk t rst reset pulse width 40 40 ns bclk baud clock 16x or 8x or 4x of data rate hz
XR16V2652 39 rev. 1.0.2 high performance duart with 32-byte fifo f igure 13. c lock t iming f igure 14. m odem i nput /o utput t iming f or c hannels a & b external clock t ech t ecl vih vil t eclk iow # rts# dtr# cd# cts# dsr# int ior# ri# t wdo t mod t mod t rsi t mod active active change of state change of state active active active change of state change of state change of state active active
XR16V2652 40 high performance duart with 32-byte fifo rev. 1.0.2 f igure 15. d ata b us r ead t iming f igure 16. d ata b us w rite t iming t as t dd t ah t rd t rdv t dy t dd t rdv t ah t as t cs valid address valid address valid data valid data a0-a2 cs# ior# d0-d7 rdtm t cs t rd 16write t as t dh t ah t wr t ds t dy t dh t ds t ah t as t cs valid address valid address valid data valid data a0-a2 cs# iow# d0-d7 t cs t wr
XR16V2652 41 rev. 1.0.2 high performance duart with 32-byte fifo f igure 17. r eceive r eady & i nterrupt t iming [n on -fifo m ode ] for c hannels a & b f igure 18. t ransmit r eady & i nterrupt t iming [n on -fifo m ode ] for c hannels a & b rx rxrdy# ior# int d0:d7 start bit d0:d7 stop bit d0:d7 t ssr 1 byte in rhr active data ready active data ready active data ready 1 byte in rhr 1 byte in rhr t ssr t ssr rxnfm t rr t rr t rr t ssr t ssr t ssr (reading data out of rhr) tx txrdy# iow# int* d0:d7 start bit d0:d7 stop bit d0:d7 t wt txnonfifo t wt t wt t wri t wri t wri t srt t srt t srt *int is cleared when the isr is read or when data is loaded into the thr. isr is read isr is read isr is read (loading data into thr) ier[1] enabled
XR16V2652 42 high performance duart with 32-byte fifo rev. 1.0.2 f igure 19. r eceive r eady & i nterrupt t iming [fifo m ode , dma d isabled ] for c hannels a & b f igure 20. r eceive r eady & i nterrupt t iming [fifo m ode , dma e nabled ] for c hannels a & b rx rxrdy# ior# int d0:d7 s t ssr rxintdma# rx fifo fills up to rx trigger level or rx data timeout rx fifo drops below rx trigger level fifo empties first byte is received in rx fifo d0:d7 s d0:d7 t d0:d7 s d0:d7 s t d0:d7 s t t d0:d7 s t start bit stop bit t rr t rri t ssi (reading data out of rx fifo) rx rxrdy# ior# int d0:d7 s t ssr rxfifodma rx fifo fills up to rx trigger level or rx data timeout rx fifo drops below rx trigger level fifo empties d0:d7 s d0:d7 t d0:d7 s d0:d7 s t d0:d7 s t t d0:d7 s t start bit stop bit t rr t rri t ssi (reading data out of rx fifo)
XR16V2652 43 rev. 1.0.2 high performance duart with 32-byte fifo f igure 21. t ransmit r eady & i nterrupt t iming [fifo m ode , dma m ode d isabled ] for c hannels a & b f igure 22. t ransmit r eady & i nterrupt t iming [fifo m ode , dma m ode e nabled ] for c hannels a & b tx txrdy# iow# int* txdma# d0:d7 s d0:d7 t d0:d7 s d0:d7 s t d0:d7 s t t d0:d7 s t start bit stop bit t wri (unloading) (loading data into fifo) last data byte transmitted tx fifo fills up to trigger level tx fifo drops below trigger level data in tx fifo tx fifo empty t wt t srt tx fifo empty t t s t si isr is read ier[1] enabled isr is read *int is cleared when the isr is read or when tx fifo fills up to the trigger level. tx txrdy# iow# int* d0:d7 s txdma d0:d7 s d0:d7 t d0:d7 s d0:d7 s t d0:d7 s t t d0:d7 s t start bit stop bit t wri t (unloading) (loading data into fifo) last data byte transmitted tx fifo fills up to trigger level tx fifo drops below trigger level at least 1 empty location in fifo t srt tx fifo full t wt t si isr read isr read *int cleared when the isr is read or when tx fifo fills up to trigger level. ier[1] enabled
XR16V2652 44 high performance duart with 32-byte fifo rev. 1.0.2 package dimensions (44 pin plcc) note: the control dimension is the millimeter column inches millimeters symbol min max min max a 0.165 0.180 4.19 4.57 a 1 0.090 0.120 2.29 3.05 a 2 0.020 --- 0.51 --- b 0.013 0.021 0.33 0.53 b 1 0.026 0.032 0.66 0.81 c 0.008 0.013 0.19 0.32 d 0.685 0.695 17.40 17.65 d 1 0.650 0.656 16.51 16.66 d 2 0.590 0.630 14.99 16.00 d 3 0.500 typ. 12.70 typ. e 0.050 bsc 1.27 bsc h 1 0.042 0.056 1.07 1.42 h 2 0.042 0.048 1.07 1.22 r 0.025 0.045 0.64 1.14 44 lead plastic leaded chip carrier (plcc) rev. 1.00 1 d d 1 a a 1 d d 1 d 3 b a 2 b 1 e seating plane d 2 244 d 3 c r 45 x h 2 45 x h 1
XR16V2652 45 rev. 1.0.2 high performance duart with 32-byte fifo package dimensions (32 pin qfn - 5 x 5 x 0.9 mm ) note: the control dimension is in millimeter. inches millimeters symbol min max min max a 0.031 0.039 0.80 1.00 a1 0.000 0.002 0.00 0.05 a3 0.006 0.010 0.15 0.25 d 0.193 0.201 4.90 5.10 d2 0.138 0.150 3.50 3.80 b 0.007 0.012 0.18 0.30 e 0.0197 bsc 0.50 bsc l 0.012 0.020 0.35 0.45 k 0.008 - 0.20 - note: the actual center pad is metallic and the size (d2) is device-dependent with a typical tolerance of 0.3mm
46 notice exar corporation reserves the right to make changes to the products contained in this publicat ion in order to improve design, performanc e or reliability. exar corp oration assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infr ingement. charts and schedules contai ned here in are only for illustration purposes and may vary depending upon a user?s specific application. while the information in this publication has been carefully ch ecked; no responsibility, however , is assumed for inaccuracies. exar corporation does not re commend the use of any of its products in life suppo rt applications where the failure or malfunction of the product can reasonably be ex pected to cause failure of the life support system or to significantly affect its safety or effectiveness. products ar e not authorized for use in such applications unless exar corporation receives , in writing, assuranc es to its satisfaction that: (a) th e risk of injury or damage has been minimized; (b) th e user assumes all such ris ks; (c) potential liability of exar corporation is adequately protected under the circumstances. copyright 2007 exar corporation datasheet may 2007. send your uart technical inquiry with technical details to hotline: uarttechsupport@exar.com . reproduction, in part or whole, without the prior written consent of exar co rporation is prohibited. XR16V2652 high performance duart with 32-byte fifo rev. 1.0.2 revision history d ate r evision d escription june 2006 p1.0.0 preliminary datasheet. march 2007 1.0.0 final datasheet. updated ac electrical characteristics. may 2007 1.0.1 added "gnd center pad" to pin description. updated 32 pin qfn package dimen - sions drawing to show minimum "k" parameter. may 2007 1.0.2 updated "ac electrical characteristics" table and pin description table.
XR16V2652 i rev. 1.0.2 high performance duart with 32-byte fifo table of contents general description........ ................. ................ ................ ............... .............. .......... 1 a pplications ............................................................................................................................... ............... 1 f eatures ............................................................................................................................... ..................... 1 f igure 1. XR16V2652 b lock d iagram ............................................................................................................................... .......... 1 f igure 2. p in o ut a ssignment ............................................................................................................................... ...................... 2 ordering information ............................................................................................................................... 2 pin descriptions ............ ................ ................ ................. ................ ................. .......... 3 1.0 product description ........................................................................................................ .............. 6 2.0 functional descriptions .................................................................................................... .......... 7 2.1 cpu interface .............................................................................................................. .................................. 7 f igure 3. XR16V2652 d ata b us i nterconnections ................................................................................................................... 7 2.2 5-volt tolerant inputs ..................................................................................................... ......................... 7 2.3 device reset ........... .............. .............. .............. .............. ........... ........... ........... ........... .................................... 7 2.4 device identification and revi sion ............ .............. .............. .............. .............. ........... .......... .............. 7 2.5 channel a and b selection .......... .............. .............. .............. .............. ........... ........... .......... .................... 7 t able 1: c hannel a and b s elect .............................................................................................................................. ................. 8 2.6 channel a and b internal register s ............. .............. .............. .............. ........... ............ ........... .......... 8 2.7 dma mode ................................................................................................................... ...................................... 8 t able 2: txrdy# and rxrdy# o utputs in fifo and dma m ode ............................................................................................. 8 2.8 inta and intb outputs............ .............. .............. .............. .............. ............ ........... ........... ........................... 9 t able 3: inta and intb p ins o peration for t ransmitter ........................................................................................................ 9 t able 4: inta and intb p in o peration f or r eceiver ............................................................................................................... 9 2.9 crystal oscillator or external clock input........... .............. .............. ........... ............ ........... ....... 9 f igure 4. t ypical c rystal c onnections ............................................................................................................................... ..... 9 2.10 programmable baud rate generator with fractional divisor ..... .............. .............. ........ 10 f igure 5. b aud r ate g enerator ............................................................................................................................... ................ 11 t able 5: t ypical data rates with a 24 mh z crystal or external clock at 16x s ampling ................................................... 11 2.11 transmitter............................................................................................................... ................................. 12 2.11.1 transmit holding register (thr) - write only............................................................................ ............. 12 2.11.2 transmitter operation in non-fifo mode .................................................................................. ................ 12 f igure 6. t ransmitter o peration in non -fifo m ode .............................................................................................................. 12 2.11.3 transmitter operation in fifo mode ...................................................................................... ..................... 12 f igure 7. t ransmitter o peration in fifo and f low c ontrol m ode ..................................................................................... 13 2.12 receiver .................................................................................................................. ..................................... 13 2.12.1 receive holding register (rhr) - read-only .............................................................................. .............. 13 f igure 8. r eceiver o peration in non -fifo m ode .................................................................................................................... 14 f igure 9. r eceiver o peration in fifo and a uto rts f low c ontrol m ode ......................................................................... 14 2.13 auto rts (hardware) flow control .......................................................................................... ...... 15 2.14 auto rts hysteresis ...................................................................................................... ........................ 15 t able 6: a uto rts (h ardware ) f low c ontrol ........................................................................................................................ 15 2.15 auto cts flow control.................................................................................................... .................... 15 f igure 10. a uto rts and cts f low c ontrol o peration ....................................................................................................... 16 2.16 auto xon/xoff (software) flow control..................................................................................... . 17 t able 7: a uto x on /x off (s oftware ) f low c ontrol ............................................................................................................... 17 2.17 special character detect........ .............. .............. .............. .............. ........... ........... ........... ................. 17 2.18 infrared mode ......... .............. .............. .............. .............. ............ ........... ........... ......... .............................. 18 f igure 11. i nfrared t ransmit d ata e ncoding and r eceive d ata d ecoding .......................................................................... 18 2.19 sleep mode with auto wake-up . ............... .............. .............. .............. .............. ........... .......... ............ 19 2.20 internal loopback...... .............. .............. .............. .............. .............. .............. .............. ......................... 20 f igure 12. i nfrared t ransmit d ata e ncoding and r eceive d ata d ecoding .......................................................................... 20 3.0 uart internal registers.................................................................................................... ......... 21 t able 8: uart channel a and b uart internal registers ............................................................................. ......... 21 t able 9: internal registers description. s haded bits are enabled when efr b it -4=1 ......................................... 22 4.0 internal register descriptions ............................................................................................. . 23 4.1 receive holding register (rhr) - read- only ......... .............. .............. .............. ............... .............. .. 23 4.2 transmit holding register (thr) - write-only ............................................................................... 23 4.3 interrupt enable register (ier) - read/write ....... .............. .............. ............ ........... ........... .......... . 23 4.3.1 ier versus receive fifo interrupt mode operation ......................................................................... ...... 23 4.3.2 ier versus receive/transmit fifo polled mode operation.................................................................. 24
XR16V2652 ii high performance duart with 32-byte fifo rev. 1.0.2 4.4 interrupt status register (isr) - read-only ........... .............. .............. .............. .............. ............. .. 25 4.4.1 interrupt generation: .................................................................................................... .................................... 25 4.4.2 interrupt clearing: ...................................................................................................... ....................................... 25 t able 10: i nterrupt s ource and p riority l evel ..................................................................................................................... 26 4.5 fifo control register (fcr) - write-only................................................................................... ...... 26 t able 11: t ransmit and r eceive fifo t rigger t able and l evel s election .......................................................................... 27 4.6 line control register (lcr) - read/write................................................................................... ...... 27 t able 12: p arity selection .............................................................................................................................. .......................... 29 4.7 modem control register (m cr) or general purpose output s control - read/write.. 29 4.8 line status register (lsr) - read only..................................................................................... ......... 30 4.9 modem status register (msr) - read only .................................................................................... ... 31 4.10 scratch pad register (spr) - re ad/write ............. .............. .............. .............. .............. .............. .... 32 4.11 baud rate generator registers (dll, dlm and dld) - read/write ............... ............... ......... 32 t able 13: s ampling r ate s elect .............................................................................................................................. ................. 32 4.12 alternate function register (afr) - read/write ........................................................................ 32 4.13 device identification register (dvid) - read only....................................................................... 3 3 4.14 device revision regist er (drev) - read only ............................................................................... .. 33 4.15 enhanced feature register (efr) . ............ .............. .............. .............. .............. ........... ........... .......... 33 t able 14: s oftware f low c ontrol f unctions ........................................................................................................................ 34 4.15.1 software flow control registers (xof f1, xoff2, xon1, xon2) - read/write .............................. 35 t able 15: uart reset conditions for channel a and b ................................................................................ ............ 36 absolute maximum ratings........... ................ ................ ............... .............. .......... 37 typical package thermal resistance data (margin of error: 15%) 37 electrical characteristics ........ ................ ................ ............... .............. .......... 37 dc e lectrical c haracteristics ............................................................................................................. 37 ta=0o to 70oc (-40o to +85oc for industrial grade package), vcc is 2.25v to 3.6v ..... .............. .............. ............ 37 ac e lectrical c haracteristics ............................................................................................................. 38 unless otherwise noted: ta = -40o to +85oc, vcc=2.25 - 3. 63v, 70 pf load where applic able ............... ............... 38 f igure 13. c lock t iming ............................................................................................................................... .............................. 39 f igure 14. m odem i nput /o utput t iming f or c hannels a & b ................................................................................................. 39 f igure 16. d ata b us w rite t iming ............................................................................................................................... .............. 40 f igure 15. d ata b us r ead t iming ............................................................................................................................... ............... 40 f igure 17. r eceive r eady & i nterrupt t iming [n on -fifo m ode ] for c hannels a & b ......................................................... 41 f igure 18. t ransmit r eady & i nterrupt t iming [n on -fifo m ode ] for c hannels a & b ....................................................... 41 f igure 19. r eceive r eady & i nterrupt t iming [fifo m ode , dma d isabled ] for c hannels a & b........................................ 42 f igure 20. r eceive r eady & i nterrupt t iming [fifo m ode , dma e nabled ] for c hannels a & b......................................... 42 f igure 21. t ransmit r eady & i nterrupt t iming [fifo m ode , dma m ode d isabled ] for c hannels a & b............................ 43 f igure 22. t ransmit r eady & i nterrupt t iming [fifo m ode , dma m ode e nabled ] for c hannels a & b ............................ 43 package dimensions (44 pin plcc ) ................. .............. ............... .............. .......... 44 package dimensions (32 pin qfn - 5 x 5 x 0.9 mm ) ................. ................ ............. 45 r evision h istory ............................................................................................................................... ....... 46 table of contents........... ................. ................ ................ ............... .............. ............. i

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