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DS1678 real-time event recorde r www . maxim-ic.com general descripti o n the DS1678 real-time clock (rtc) event recorder records the time and date of a nonperio d i c, asy nchronous event each ti m e the int pin is activated. the device records the seconds, m i nutes, hours, date, day of t h e week, m o n t h, y ear, and century when the first event occurs, and starts the 16- bit elapsed time counter ( etc). subsequent events trigger the recording of t h e etc into the event-log mem o ry . this allows for up to 1025 events to b e logged. even ts can be lo gged while the device is operating fro m either v cc or v bat . pin configuration features real-time c l ock/calendar in binary-coded deci mal (bc d ) format c o unts seconds, minutes, ho urs, date, m o nth, day of the week, and year with lea p year com p ensation and is year 2000 com p liant logs up to 1025 consecutive events in read- only battery-backed me mory user -programmable eve n t trigger c a n be triggered by the falling edge, rising edge, or rising and falling ed ges of the in t pin event counter regist er p r ovides data on the num b er of events that have been logged in the current event-logging mission typical operating circui t programma ble rtc ala r m 32-byte, battery-backed, general-pu rpose nv ram i 2 c* serial interface three resol u tion options for trade- off accuracy vs. maximum time b e tw ee n events -40 c to +85 c industrial temperature range underw rite r s laboratory (ul) reco gniz ed ordering information part ? pin-pack a g e top mark ?? d s 1678 8 plast i c d i p d s 1678 d s 1678 + 8 plast i c d i p d s 1678 d s 1 6 7 8 s 8 so d s 1 6 7 8 s d s 1 6 7 8 s + 8 so d s 1 6 7 8 s d s 1678s/t& r 8 so (tape and reel) d s 1678s d s 1678s+t& r 8 so (tape and reel) d s 1678s to p view ? all devices are specified over the -40c to +85 c operating range. ?? a ? ? + ? anyw h e r e on the t op m a r k denotes a lead- free device. + denotes a lead -free/r o hs-co m pliant device. * i 2 c is a tr adem a r k of philips cor p . pur c hase of i 2 c componen ts fro m maxim inte grated prod ucts, inc., or one of its sub licensed associated companies, convey s a license under the philips i 2 c patent rights to use these co m p o nents in an i 2 c s ystem , pr ovided that the system confor m s to the i 2 c standard specification as defined by philip s. x1 v cc 1 8 2 7 DS1678 i nt x2 v bat scl 3 6 gnd 4 5 sda pdip (300 mils) so (208 mils ) 1 o f 25 rev : 100 405
DS1678 real-tim e event re corder absolute m a xi mum ratings voltage range on any pin relative to ground?????????????????..-0.3v to +6.0v operating t e m p erature range (noncondensing)????????????????...-40c to +85c storage temperature r a nge???????????????????????.?-55c to +125c soldering t e m p erature????????????????.see ip c/jedec j-std-020 specification this is a stress rating onl y and fu nctional ope rat i on of the device at th ese or an y o t her cond itions a bove those indicated in t h e op eration sections o f th is s p ecifica tion is n o t implied. expo sure to absolute maximum ra ting conditions for extend ed p e riods of tim e may aff e ct d evi ce reliabil ity . recommended dc oper ating conditions (v cc = v cc (m in ) to v cc(max ) , t a = -40c to +85c, unless other wise noted. typical values are at no minal supply voltage and t a = +25 q c, unless otherwise noted.) (note 1) parame t e r s y m b o l con d it i o n s m i n t y p max u n i t s power-suppl y voltage v cc ( n o t e 2 ) 4 . 5 5 . 0 5 . 5 v input l ogic 1 v ih ( n o t e 2 ) 2 . 2 v cc + 0.3 v input l ogic 0 v il ( n o t e 2 ) - 0 . 3 + 0 . 8 v pullup resistor value v pu v cc = 0v (note 2) 5.5 v battery voltage v bat ( n o t e 2 ) 2 . 6 3 . 5 v dc electrical characteristics ( v cc = v cc (mi n ) to v cc(m a x ) , t a = -40c to +85c.) parame t e r s y m b o l con d it i o n s m i n t y p max units sda, scl sda output off -1 +1 input leakag e int i li int output of f 1 0 p a logic 0 outp ut i ol = 4 m a (s da, int ) v ol 0 . 4 v active suppl y current i cca 1 2 m a power-fail voltage (note 2) v pf v bat = 3.0v 1.21 6 x v bat 1.25 x v bat 1.28 4 x v bat v lobat trip point lobat trp 1 . 3 5 dc electrical characteristics ( v cc = 0v , t a = -40c to +85c.) (no t e 1) parame t e r s y m b o l con d it i o n s m i n t y p max units v bat current (oscillator on) i osc 3 0 0 5 0 0 n a v bat current (oscillator off) i bat 5 0 1 5 0 n a 2 of 2 5
DS1678 real-tim e event re corder ac electrical characteristics ( v cc = 2.6v to 5.5v or v ba t = 2.6v to 3.5v , t a = -40c to +85c.) (note 1) parame t e r s y m b o l con d it i o n s m i n t y p max u n i t s input capacitance c i int 1 0 p f minim u m signal width t glitch 0.12 2 0.24 5 m s m i n i mu m e v e n t r a t e t event 0.85 4 1 . 2 2 m s ac electrical characteristics ( v cc = 4.5v to 5.5v , t a = -40 q c to +85 q c.) (note 1) parame t e r s y m b o l con d it i o n s m i n t y p max u n i t s fast m ode 100 400 scl clock frequency f scl standard m ode 100 khz fast m ode 1.3 bus free ti me betw een a stop and start condition t buf standard m ode 4.7 p s fast m ode 0.6 hold tim e ( r epeated) st art condition (note 3) t hd: sta standard m ode 4.0 p s fast m ode 1.3 low period of scl t lo w standard m ode 4.7 p s fast m ode 0.6 high period of scl t high standard m ode 4.0 p s fast m ode 0.6 setup tim e f o r a repeated start t su:sta standard m ode 4.7 p s fast m ode 0 0.9 data hold time (note 4) t hd: dat standard m ode 0 p s fast m ode 100 data setup time (note 5) t su: dat standard m ode 250 ns fast m ode 20 + 0.1c b 3 0 0 rise ti me of both sda and scl signals (note 6) t r standard m ode 20 + 0.1c b 1 0 0 0 ns fast m ode 20 + 0.1c b 3 0 0 fall ti m e of both sda and scl signals (note 6) t f standard m ode 20 + 0.1c b 3 0 0 ns fast m ode 0.6 setup tim e for stop t su:sto standard m ode 4.0 p s capacitive l o ad for each bus line (note 6) c b 4 0 0 p f input capacitance (scl, sda) c i 5 p f warning : under no circumstances are negati ve undershoots of an y am plitude allow e d w h en the device is in w r ite protect. 3 of 2 5
DS1678 real-tim e event re corder 4 of 2 5 note 1: lim its a t -40 ? ?
DS1678 real-tim e event re corder 5 of 2 5 block diagram dallas se m i conductor DS1678 c l c l divider x2 x1 oscillat o r gnd 2048 0 data log ram port 000h address register i nt co ntr o l logic user ram 7ffh real-time clo c k scl sda i 2 c serial interfa c e v bat v cc power co ntr o l 1hz datalo g nv sram
DS1678 real-tim e event re corder 6 of 2 5 pin description pin name function 1, 2 x1, x2 connections for standard 32.768khz quartz crystal. for greatest accuracy, the DS1678 must be used with a crystal that has a specified load capacitance of 12.5pf. there is no need for external capacitors or resistors. note: x1 and x2 are very high-impedance nodes. it is recommended that they and the crystal be isolated from high-freque ncy signals. for more information on crystal selection and crystal la yout considerations, refer to application note 58: crystal considerations with dallas real-time clocks . 3 v bat battery input for standard lithiu m cell or other energy source. all functions of the DS1678 with the excep tion of the serial interface circuitry are powered by v bat when v cc < v bat . all functions are powered by v cc when v cc > v bat . the serial interface is enabled when v cc is above v pf . if a battery or other energy source is not used, v bat should be connected directly to ground. diodes must not be placed between the battery and the v bat input or improper operation results. ul recognized to ensure against reverse charging current when used w ith a lithium battery. see ?conditions of acceptability? at www.maxim-ic.com/qa/info/ul/ . 4 gnd ground 5 sda serial data input/output. sda is the data input/output (i/o) signal for the i 2 c serial interface. the sda pin is an open-drain i/o and requires an external pullup resistor. 6 scl serial clock input. scl is used to synchronize data movement on the serial interface. it requires an external pullup resistor. 7 int active-low interrupt input/output. the int pin is an i/o that is activated by an external device to signify an ev ent has occurred and should be logged. once the pin is activated, the event is recorded in the event-log memory and the event counter register is incremented. the trx bits determine which input edge(s) trigger an event: an even t can be triggered by a falling edge on the int pin, a rising edge, or by bot h the rising and falling edges. the int pin can also be used as an output when the DS1678 is not in an event-logging mission. the int pin becomes an output and generates an alarm interrupt if the disx bits are set to zero and the rtc reaches the preset value in the alarm register. the int output remains low as long as the status bit causing the interrupt is present and the disx bits are set to zero. the int pin is an open-drain input/output with a weak internal pulldown resistor to prevent the pin from fl oating when the pin is tri-stated. 8 v cc dc power for primary power supply
DS1678 real-tim e event re corder 7 of 2 5 detailed description the event counter register contains the total number of events that have been logge d in the current event-logging mission. the event counter register also allows the user to determine if the data in the event-log memory has rolled over. the 16-bit etc can be incremented once per second, once per minute, or once per hour. each event transfers the current etc value into the event-log me mory, then clears and restarts the etc. the three increment periods allow users to maximize the reso lution while providing an adequate maximum time between events. the seconds resolution provides the time of an event down to the sec ond, while allowing up to 65,535 seconds (18.2 hours) between events without using additional event-log memory. the minutes resolution provides the time of an event down to the minute, while allowing up to 45.5 days between events without us ing extra memory locations. the hours re solution provides the time of an event down to the hour in which it occurred, while allo wing up to 7.5 years between events without using additional event-log memory. based on the expected fr equency of events, an increment period can be selected to maximize the resolution while minimizing use of th e event-log memory. the event can be triggered in thre e different ways depending on how th e user programs the trigger select (trx) bits in the control register. the event can be triggered by a falling edge on the int pin only, a rising edge only, or it can be triggered by rising a nd falling edges. triggering with both the rising and falling edges allows for monitoring when something is turned on/off and how long it is in either state. the rtc provides seconds, minutes, hours, day, date , month, and year information with leap-year compensation, and year 2000 compliance. the rt c also provides an alarm interrupt. the i 2 c interface allows the rtc to function as a stand-alone rtc in the system. the programmable alarm trip points in the rtc allow a flag to be set in the c ontrol register when the specified time in the alarm trip point register is reached. the flag is readable via the i 2 c interface during an event-logging mission or, wh en the DS1678 is not in a mission, int becomes an output and generates an alarm interrupt if the value in the rtc equals the value in the rt c alarm register and the duration interval select (disx) bits are both set to zeros. the DS1678 operates as a slave device on the i 2 c serial bus. access is obt ained by generating a start condition and providing a de vice identification code. all data is transferred to and from the DS1678 most significant bit (msb) first. the addre ss counter automatically increments so that subsequent registers can be accessed sequentially until a stop condition is executed. when v cc falls below 1.25 x v bat , the device automatically write prot ects itself by disabling the i 2 c interface, terminates any access in progress, and resets the device address counte r. inputs to the device via the i 2 c bus are not recogni zed at this time in order to prevent erroneous data from being written to the device from an out-of-tolerance system. when v cc falls below v bat , the device switches into a low-cu rrent battery-backup mode. upon power- up, the device switches from battery power to v cc when v cc is greater than v bat + 0.2v, and recognizes inputs from the system when v cc is greater than 1.25 x v bat by releasing control of the write protection on the i 2 c bus. the block diagram shows the main elements of the rtc ev ent recorder. the device has four major components: a 64-bit rtc and control block, 32-byt e user nv ram, 2048 bytes of event-log memory (1024 events), and an i 2 c serial interface.
DS1678 real-tim e event re corder 8 of 2 5 pow e r control the device is fully acces sible and data can be written and read when v cc is greater than v pf . however, when v cc falls b e low v pf , the internal reg i sters are b l ocked from any access. the device power is switched from v cc to v bat when v cc drops below v bat . operation, except for the i 2 c in terface, is m a intained f r om the v ba t source until v cc is r e turned to n o m i nal levels (table 1). af ter v cc return s above v pf , read and write acces s is allowed. table 1. pow e r control supply conditi on read/write access powere d by v cc < v pf , v cc < v bat n o v bat v cc < v pf , v cc > v bat n o v cc v cc > v pf , v cc > v bat y e s v cc oscillator ci rcui t the DS1678 uses an external 32.768khz crystal. the oscillator circuit does not require any external resis t ors or capacitors (c l ) to operate. table 2 specifies several crys tal param e ters for the extern al c r ysta l, and the oscillator block in the block diagram shows a functional schem a tic of the oscillator circuit. using a crystal with the specified characteristics, th e startup tim e is usually less than one second. table 2. crystal specifications* param et e r s y m b o l m i n t y p m a x u n i t s nom i nal frequency f o 3 2 . 7 6 8 k h z series res i s t ance esr 45 k : load capacitance c l 1 2 . 5 p f * the crystal, traces, and crystal in put pins should be isolated from r f gener ating signals. refer to application note 58: cr y s t a l considerations for d a llas real-time cl ocks for additional s pecifications. clock accuracy the accu racy of the clo c k is depen d ent upon the accu racy of the crystal and the accuracy of the m a tch between the capacitive load of the oscillato r circui t and th e capacitive load f o r which the cry s tal wa s trimm e d. addition a l er ror is add e d by crys ta l f r eque ncy drif t cau sed by tem p erature shif ts. externa l circuit noise coupled into the osci llator circuit can resu lt in the clock running fast. figure 1 shows a typical pc board layout for crystal and os cilla tor isola tion f r om noise. ref e r to a pplica tion note 5 8 : crystal con s iderations w ith dallas real-time c l ocks for detailed information. figure 1. typical cr ystal lay o u t gnd x2 x1 cr y s tal l o ca l ground p l ane (l a y e r 2 )
DS1678 real-tim e event re corder 9 of 2 5 memory the memory map in figure 2 shows th e general organization of the DS1678. as can be seen in the figure, the device memory is in one contiguous segment with a data port to access the event-log memory. because the i 2 c bus is limited to a maximum of 256 addresse s (one byte), the DS1678 uses the data port to access the 2048 bytes of ev ent-log memory. the address that the ne xt data would have been written to before logging was stopped is stored in the addre ss pointer register lsb (3fh) and msb (40h). these data bytes are used to recover all the data after a rollover occurs. the data l og address pointer points to the oldest event in the memory after a rollover. this is the memory location in event-log memory that would be overwritten by the next ev ent. read the data from this point to the end of the memory and the start time stamp, including the two-byte etc from the last event. working backward from the value in the start time stamp, subtract the value in the etc from the last event to get the time the last event in the memory occurred. then subtract the values in each of the two-byte memory locations for elapsed time between events to recover the time the previous event occurred. the value in the etc register lsb (3dh) and msb (3eh ) is the value in the actual etc. this is the time from the last event recorded until logging was stopped. since a new event has not occurred, this data has not been stored in the event memory yet. the data port is made up of three bytes. the first byte (41h) is the event-log memory address lsb, the second byte (42h) is the event-log memory address msb, and the third byte (43h) is the event-log memory data byte. to access da ta via the data port, an i 2 c write to the lsb of th e event log lsb (41h) is performed, writing the appropriate lsb address information. the i 2 c register pointer automatically increments to the event-log memory address msb (42h), where a second i 2 c write is performed, writing the msb address information. the i 2 c register pointer automatically increments to the event-log data byte address (43h). a repeated start, followed by the i 2 c slave address with a read command (1) in the r/ w bit of the i 2 c address byte is performed. subsequent read cycles reads the event-log information in the event-log memory. for each read, the event-log memory address poi nter in main memory locations 41h and 42h is autoincremented to the next higher event-log memory address, while the pointer for the main memory remains at location 43h. this allows the event-log memory to be read con tinuously without having to write the next desired event-log memory location prio r to each data read. the ev en address locations in the event-log memory correspond to the lsb of the elapsed time between events, and the odd memory locations correspond to the msb of the elapsed time between events. see table 3 for more information about how the data is stored in the event-log memory. when the event-log memory address pointer gets to the last address location (07ffh), the automatic incrementing stops. a new starting address must then be written into the event-log memory pointer bytes (41h and 42h) to begin reading addi tional data. the event-log memory a ddresses that can be put into the pointer (41h and 42h) are 0000h to 07ffh. the five ms bs of the address are i gnored. entering a value greater than 07ffh results in the ad dress location associated with the va lue of the lowest 11 bits of the address. the rtc and control registers (see fi gure 2 for more details) are located in the main memory between addresses 00h and 0fh. the user nv ram resides in locations 10h through 2fh. the event-logging memory data port is located at locations 41h, 42h, a nd 43h. memory locations 44h and up are reserved for future extensions and read 00h.
DS1678 real-tim e event re corder 1 0 of 25 the user can write only to the rtc, control registers, and user nv ram. the rest of the memory map is read-only from the user?s perspective. during an ev ent-log mission, all the memory is read-only. a write terminates the mission. if there is an event being recorded when the mission is terminated, the event finishes being recorded before the mission is stopped, and the values in the mip and me bits do not change to zeros until the mission is complete. during an event-log mission, memory locations 30h and ab ove are not accessible to the user to avoid data collisions from a user read and an event being logged at the same time. if the user tries to read a location with an address greater than 2fh duri ng a mission, the value returned is 00h. table 3. DS1678 event elapsed time duration address register 0000 event 1 elapsed time from last event counter lsb 0001 event 1 elapsed time from last event counter msb 0002 event 2 elapsed time from last event counter lsb 0003 event 2 elapsed time from last event counter msb 0004 p 07fb p 07fc event 1023 elapsed time from last event counter lsb 07fd event 1023 elapsed time from last event counter msb 07fe event 1024 elapsed time from last event counter lsb 07ff event 1024 elapsed time from last event counter msb
DS1678 real-tim e event re corder 1 1 of 25 figure 2. DS1678 rtc and control page msb lsb address bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 function 00 0 10 seconds seconds 01 0 10 minutes minutes am /pm 02 0 12/ 24 10 hr 10 hr hour 03 0 0 0 0 0 day of week 04 0 0 10 date date 05 0 0 0 10 mo month 06 10 year year 07 10 century century rtc 08 ms 10 seconds alarm seconds alarm 09 mm 10 minutes alarm minutes alarm am /pm 0a mh 12/ 24 10 hr 10 hr hour alarm 0b md 0 0 0 0 day-of-week alarm rtc alarm 0c 0d (reads 00h) reserved 0e me clr dis1 dis0 ro tr1 tr0 eosc control 0f 0 mem clr mip cm lobat rof 0 almf status 10 11 12 ; 2f byte 1 byte 2 byte 3 ; byte 32 user- programmable nv memory higher addresses read back as 00 h while a mission is in progress. 30 0 10 seconds seconds 31 0 10 minutes minutes am /pm 32 0 12/ 24 10 hr 10 hr hours 33 0 0 0 0 0 day-of-week 34 0 0 10 date date 35 0 0 0 10 mo month 36 10 year year 37 10 century century time stamp 38 event 0 elapsed time from last event counter lsb 39 event 0 elapsed time from last event counter msb event 0 rollover stamp 3a low byte 3b medium byte 3c high byte event counter 3d low byte 3e high byte elapsed time counter (etc) 3f low address byte 40 high address byte address pointer 41 low address byte 42 high address byte 43 data byte data log ram port 44 ; ff (reads 00h) reserved
DS1678 real-tim e event re corder 1 2 of 25 event logging when the DS1678 event-logging function is enabled, the device is said to be on an ?event-log mission? until the event logging is stopped. an event can be triggered one of three ways dependi ng on the settings of the trx bits in the control register. with the tr0 bit set to one and the tr1 b it set to zero, int is activated on the falling edge of the input signal. with the tr0 bit set to zero and the tr 1 bit set to one, int is activated on the rising edge of the input signal. with bot h tr0 and tr1 bits set to one, int is activated on both the falling and rising edges to allow for the measurement and duration of on/off type events. if tr0 and tr1 are both set to zero, nothing happens when int is toggled, and a mission does not start. this is an illegal state and the mission does not start without a valid value in the trx bits prior to attempting to start the mission. during an event-log mission, every time int is activated, the elapsed time from the last event is written to the event-log memory pages. these memory page s are accessible through the data port in the main memory. to access data via the data port, the lsb of the address location in the event-log memory is written into 41h, the main memory address pointer au tomatically increments to 42h where the event-log memory address msb data is written. the data from the event-log memory lo cation corresponding to the address written into main memory locations 41h a nd 42h is available in loca tion 43h to be read. the event-log data is located at addresses 0000h?07ffh in the event-log memory. the lsb of the first event duration is written to address location 0000h. the msb of the first event duration is written to address location 0001h. the lsb of the second event is written to address location 0002h. the msb of the second event duration is written to address location 0003h (see table 3 for more details). likewise, the address is incremented with each a dditional event duration. a total of 2048 registers have been reserved for event-log data, which allo w 1024 events to be logged. an event-log mission can be initiated by two methods (figure 3). the first method to start a mission is with a delayed start. this is accomplished by writing a one to the me bit. the mission starts when the first event occurs by activating int . when int is activated, the mip bit in the status register is set to one, the current time/date is written to the start ti me stamp register, and the event 0 rollover stamp is written to zero. the event counter register is incr emented and the etc starts. subsequent events are logged as the duration of time from the previous even t by writing the contents of the etc into the event- log memory when that subsequent event is triggered by the activated int pin. note: the me bit can only be written to one and a mission started if the mem clr bit is set to one. the second way to start a mission is write a one to the mip bit of the status register over the i 2 c interface. when mip is written to on e, the me bit in the control regi ster is automatically set to one. when the mip bit is written to one, the mission is st arted by loading the current time/date into the start time stamp, and the event 0 rollover stamp is wr itten to zero. the even t counter register is incremented and the etc starts incrementing. the first event is then logged as the duration of time since the start time. all subsequent even ts are then logged as the duration of time since the previous event. note: the mip bit can only be written to one and a mission started if the mem clr bit is set to one. the mem clr bit of the status register must be a one to start an event-log mission. this means that the event-log memory, event count, etc, address pointer, and start time stamp registers are cleared of data (all zeros) so that an end user cannot turn the logger on and o ff to avoid recording events. once the mission is stopped, the memory must be cleared to start a new mission.
DS1678 real-tim e event re corder 1 3 of 25 figure 3. s t art mission flow chart ye s s t a r t vi a c o m pute r s t a r t vi a ex t e r n a l ev e n t me m cl r =1 no c l ear me m o r y w r i t e a 1 t o th e m i p bi t t h e m e bi t i s a u t o m at i c al l y wr i tte n to a 1 t i m e / d a t e s t am p is w r it te n etc s t a r t s i n cr e m en t i n g ec i s i n cr e m en t e d ye s i n t i npu t ac tiv a t e d no c o n t i nue to m o n ito r i n p u t r e c o r d e v e n t in ev e n t m e m o r y ye s me m cl r =1 no c l ear me m o r y w r i t e a 1 t o th e m e bi t . mi p = 0 ye s i n t i npu t ac tiv a t e d no c o n t i nue to m o n ito r i n p u t m i p a u t o m at i cal l y wr i tte n to a 1 t i m e / d a t e s t am p i s wr i tte n etc s t a r t s i n cr e m en t i n g . ec i s i n cr e m en t e d ye s i n t i npu t ac tiv a t e d no c o n t i nue to m o n ito r i n p u t r e c o r d e v e n t in ev e n t m e m o r y etc i s c l ear ed etc i s c l ear ed
DS1678 real-tim e event re corder 1 4 of 25 rollover handling there are two options for dealing with the potential occurrence of a data overrun (i.e., more than 1024 total event logs in the event-log memory) (figure 4) . the first option is to enable rollovers. this is accomplished by setting the rollover bit (bit 3 of the control register) to one. when rollover is enabled, new data is written over previous da ta, starting with the start time stam p register, as if a new mission is starting. when a rollover occurs, the event 0 rollover stamp has the elapsed time since event 1024 of the event- log memory. this is to allow the user to recover the in formation recorded prior to the rollover. at the start of a mission, the event 0 rollover stamp data is zero, as there was no previous ev ent from which to have an elapsed time. when 1024 events are recorded in the event-log memo ry, the next event causes a new time/date stamp to be written to the start time stamp register and th e elapsed time since event 1024 written to the event 0 rollover stamp. the new event is writte n to the first location in the ev ent log, overwriting the old data, and the address pointer is incremented. when the rollove r occurs, the rollover flag (rof) in the control register is set to one to i ndicate that the memory has rolled over at least one time. the second option for dealing with data overrun is to disable rollovers by setting the rollover bit to 0. the DS1678 stops recording after event 1025, and the addr ess pointer is incremented from 07ffh to 0000h. the device continues monitoring int and the event counter continues to increment when int is activated, even though the event-log memory has been filled. a time stamp for the first event is recorded after a mission begins. the time of acquisition for subsequent events is determined by considering the start time recorded by the time stamp; the value in the event counter register, rof; and the address of the part icular data sample in the event-log memory. if no rollover has occurred in the event-log memory (rof = 0), the sample time associated with any particular data point can be calculated by multiplying the sum of the elapsed time between the events up to that event by one second, minute, or hour depending on which resolution is selected in th e disx bits of the control register, and adding this elapsed time to the value in the start time stamp register. if rollover has been enabled, the user can determine if rollover has occurred by reading the value in the event counter register or the rof. the event counter register counts the total number of events that have been acquired. if this value is greater than 0400h (decimal 1025), then the user knows that rollover has occurred. if rollover ha s occurred, the user needs to determ ine how many times rollover occurred in determining the sample time for any particular data sa mple. the address pointer points to the oldest data in the event-log memory, and, if the memory has rolled over at least one time, the rollover flag is set to one. the DS1678 has been designed so the user cannot directly write to the event-log memory. this prevents writing invalid data to th e event-log registers.
DS1678 real-tim e event re corder 1 5 of 25 figure 4. rollover flow chart ye s ec is i n cr e m en t e d ye s in t i npu t a c tiv ate d no co n t i nue t o m o n ito r i n p u t ye s me m o r y fu l l no etc w r i tte n to ev e n t 0 an d t i m e / d a t e s t am p is w r itte n r o llo v e r en a b l e = 1 etc is c l ear ed r eco r d ev e n t i n ev e n t m e mo r y no
DS1678 real-tim e event re corder 1 6 of 25 clock, calendar, and alarm the time and calendar information is accessed by reading/ writing the appropriate register bytes. note that some bits are set to zero. these bits always read zer o regardless of how they are written. the contents of the time, calendar, and alarm registers are in the bcd format and are year 2000 compliant. the DS1678 can run in either 12-hour or 24-hour mode. bit 6 of the hours re gister is defined as the 12- or 24-hour mode select bit. when hig h, the 12-hour mode is selected. in the 12-hour mode, bit 5 is the am /pm bit with logic one being pm. in the 24-hour mode, bit 5 is the second 10-hour bit (20?23 hours). the day register increments at midnight. values that correspond to the day of week are user defined, but must be sequential, e.g., if 1 equals sunday, then 2 equals monday, and so on. illogical time and date entries result in undefined operation. when reading or writing the time and date registers, secondary (user) bu ffers are used to prevent errors when the internal registers update. when reading th e time and date registers, the user buffers are synchronized to the internal registers on an i 2 c start. the time and calendar information is read from these secondary registers, while th e clock continues to run. the countdo wn chain is reset whenever the seconds register is written. write transfers oc cur on the acknowledge from the device. once the countdown chain is reset, to avoid ro llover issues the remaining time a nd date registers must be written within one second. the DS1678 also contains a time-of-day alarm. the al arm registers are located in registers 08h?0bh. bit 7 of each of the alarm registers is a mask bit (table 4). when all the mask bits are logic zero, an alarm occurs once per week when the values stored in ti mekeeping registers 00h?03h matc h the values stored in the time-of-day alarm registers. an alarm is generated every day when the mask bit of the day alarm register is set to one. an alarm is generated every hour when the day an d hour alarm mask bits are set to one. similarly, an alarm is generated every minute wh en the day, hour, and minute alarm mask bits are set to one. an alarm occurs every second when the day, hour, minute, and seconds alarm mask bits are set to one. as a security measure to prevent unauthori zed tampering, writing to any memory location or changing any value in the rtc and control registers stop an event-log mission and clear the mip bit to zero. table 4. time-of-day alarm bits alarm register mask bits (bit 7) seconds (ms) minutes (mm) hours (mh) days (md) description 1 1 1 1 alarm once per second 0 1 1 1 alarm when seconds match 0 0 1 1 alarm when minutes and seconds match 0 0 0 1 alarm when hours, minutes, and seconds match 0 0 0 0 alarm when day, hours, minutes, and seconds match
DS1678 real-tim e event re corder 1 7 of 25 special-purpose registers the following descriptions define the operatio n of the DS1678 special-purpose registers. control register (0eh) m s b l s b bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 me clr dis1 dis0 ro tr1 tr0 eosc bit 7: mission enable (me). this bit enables the device to begin a mission. the me bit cannot be written to one unless the mem clr bit in the status register is one, signify ing that the memory and registers have been cleared. with the me bit set to one, the device waits for the first event to occur ( int is activated). once that first event occurs, the mip bit is set, the time/date stamp is recorded in the start time stamp register, the event 0 rollover stamp is written to zero, the even t counter register is incremented, and the etc begins incrementing. when the me bit is set to logic zero, the DS1678 wa its until a one is written to the mip bit via the i 2 c interface to start the mission. when th e mip bit is written to one, the me bit is set to one, the current time/date is recorded in the start time stamp regist er, the event 0 rollover stamp is written to zero, the event counter register is incremen ted, and the etc begins incrementing. the me bit is automatically written to zero whenever a mission is stopped. bit 6: clear enable (clr). this bit enables the memory to be clear ed. when this bit is set to logic one and the clear memory (cm) bit is subsequently se t to one, the event-log memory, event counter, and start time stamp registers are all cleared to zeros. fo llowing the writing of a one to the me bit, the clr bit is also set to logic zero, and th e mem clr bit is set to logic one. if the clear enable bit is set, but a command other than writing a one to the clear memory bit is issued ne xt, the clr bit is cleared to zero and the contents of the event-log, start time stamp, and event counter registers are unchanged. bits 5 and 4: duration interval select 1 and 0 (dis1 and dis0). these bits select the amount of time between increments of the etc that is used to determin e the amount of time between events. after the first event is recorded, all subsequent events are r ecorded as the elapsed time since the previous event. when a subsequent event occurs, the etc va lue is stored in the event-log memory. to obtain the maximum accuracy of the event logger, the smallest possible resolution of the etc should be selected. the expected maximum time between events must also be taken into account to get the full 1025 events logged, because when the etc count reac hes 65,535 increments, if the next event has not occurred by that point, ffffh is written into the memory, the etc rolls over to 0000h and continues to count until the next event occurs or ffffh is reach ed again. whenever ffffh is reached by the etc, it stores that value in event-log memory, resets to 0000h, continues counting, and the memory address pointer increments to the next memory location. whenever an ffffh appears in the memory, the next two bytes of data are part of the elapsed time for the sa me event, even if the valu e in the next two bytes of memory are 0000h, which means that an event occurr ed at time increment ffffh. to recover the total elapsed time between events when ffffh is in the ev ent-log memory; add the contents of the next two bytes to the ffffh. if the next tw o bytes are 0000h, indicating that the event occurred at ffffh, add the 0000h to ffffh to get ffffh. if the next two bytes are 0100h, add 0100h to ffffh to get 100ffh. this
DS1678 real-tim e event re corder 1 8 of 25 represents the total elapsed time since the previous ev ent. the event counter is not incremented when the etc rolls over because a new event has not occurred. the etc is incremented as the selected seconds, minutes, or hours register of the rtc increments. because the rtc continues to run, ev en when the etc is cleared to pr epare for a new event, and the etc is incremented every time the selected byte in the rt c increments, the actual time resolution is not lost even when events occur more frequently than the minimum time resolution selected. if an event occurs half way between increments of the etc, the first in crement of the next event occurs when the seconds, minutes, or hours register increments next, thus preserving the correct time to the resolution selected in the disx bits. when the alarm interrupt output is used, the disx bits should be set to zeros. an event-logging mission cannot be started if the disx bits ar e set to zero. this enable s the alarm flag to generate an alarm interrupt via the int output pin. with the dis0 bit set to one and the dis1 bit set to zero, the etc increments every time the seconds register in the rtc is incremented. this gives th e maximum resolution between events, but the counter rolls over to the next two memory bytes when it reaches the maximum value. the largest interval between events that can be accurately m easured without using additional me mory space and reducing the total number of events able to be logged is 65,535 sec onds, or about 18.2 hours. if the maximum time between events could be greater than 18.2 hours, consider using one of the courser resoluti ons to conserve memory. with the dis0 bit set to zero and the dis1 bit set to one, the etc increments every time the minutes register in the rtc is incremented. this gives a medium resolution between events, but increases the largest possible inte rval between events th at can be accura tely measured without using additional memory space and reduces the total number of events able to be logged to 65,535 minutes, or about 45.5 days. with both disx bits set to one, the etc increments every time the single hours byte in the rtc is incremented. this gives the lowest resolution between events, but increases the largest possible interval between events that can be accurately measured w ithout using additional memory space and reduces the total number of events able to be logg ed to 65,535 hours, or about 7.5 years. if a second event occurs before the etc is able to increment for the fi rst time, all zeros are logged in the event-log memory and the etc resets. if this occurs, the time base remains correct as it is based on the separate rtc incrementing, but the exact time of the even t is no more accurate than the size of the time increment that is chosen. for this reason, it is recommende d to use the finest re solution possible for your logging to minimize the errors. if the normal duration be tween events is several days or months, then a few minutes or an hour may not be significant to your data accuracy. table 5. duration interval select bits dis1 dis0 elapsed time count resolution max time between events 0 0 alarm interrupt output enabled ? 0 1 counter increments every second 18.2 hours 1 0 counter increments every minute 45.5 days 1 1 counter increments every hour 7.5 years
DS1678 real-tim e event re corder 1 9 of 25 bit 3: rollover (ro). this bit determines whether the data l og function of the DS1678 rolls over or stops writing data to the event-log memory if the event-log me mory is completely filled. if ro is set to one, the event-log memory rolls over after all 2048 bytes in the event-log memory have been used. after the 1024th event recorded in the event-log memory, th e following sample has the full time/date stamp information written to the start time stamp register and the contents of the etc written to the two bytes following the start time stamp (event 0 rollover stam p). the next sample has the duration of time from the new start time stamp value written to event-log memory address locations 0000h and 0001h, overwriting the original data. like wise, subsequent samples increment through the event-log registers, overwriting their data. the event 0 rollover stamp has the elapsed time since th e last event in the event-log memory. this is to allow the user to recover the information prior to the rollover. at the start of a mission, the value in these two bytes is zero since there was no previous event from which to ha ve an elapsed time. if ro is set to zero, no further event logs are written to the event-log memory after all event-log memory registers have been filled. however, events continue to be recognized, and the event count er register is incremented for each event. bits 2 and 1: trigger sel ect 0 and 1 (tr1 and tr0). these bits select th e edge(s) that activate int to cause an event to be logged. an event can be triggere d one of three ways, dependi ng on the set tings of the trx bits in the control register. with tr0 set to one and tr1 set to zero, int is activated on the falling edge of the input signal. with tr0 set to zero and tr 1 set to one, the int is activated on the rising edge of the input signal. with tr0 and tr1 set to zero, int is activated by the rising and falling edges to allow for the measurement and duration of on/off type events. if tr0 and tr1 are set to zero, nothing happens when int is toggled, and a mission does not start. this is an illegal state, and the mi ssion does not start without a valid value in the trx bits prio r to attempting to start the mission. table 6. trigger select bits tr1 tr0 edge(s) used to trigger an event 0 0 nothing, illegal state 0 1 falling edge 1 0 rising edge 1 1 both rising and falling edges bit 0: enable oscillator (eosc). this bit allows the clock oscillator to shut off to save power. the rtc no longer keeps time when the oscillator is shut off, but the information stored in the device memory is maintained. an event-log mission cannot start with eosc set to zero, a nd the rtc must be reset to the correct value after the oscillator is restarted and prior to starting a mission to obtain good data. a clear memory also cannot be executed wit hout the oscillator running. when v cc > v bat , the oscillator automatically starts, no matter what the value in the eosc bit, to allow proper communications. disabling the oscillator with eosc can be used to extend the battery life whenever time and date operation on battery backup is not required.
DS1678 real-tim e event re corder 2 0 of 25 status register (0fh) msb lsb bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 0 mem clr mip cm lobat rof 0 almf bit 6: memory cleared (mem clr). this bit indicates that the event-log memory, event counter, and start time stamp registers are all cleared to zer o. mem clr is cleared to zero when an event-log mission is started (i.e., mip = 1). bit 5: mission in progress (mip). this bit indicates the sampling st atus of the DS1678. if mip is logic one, the device is currently on a ?mission? in which it is operating in the ev ent-logging mode. the mip bit is changed to logic one imme diately following the activation of int if the me bit of the control register contains a one. to immediately start an event-logging mission via the i 2 c bus, a one can be written into the mip bit and a one is automatically written into the me bit of the control register. if mip is logic zero, the DS1678 is not currently in event-logging mode. the mip bit transitions from logic one to logic zero whenever event logging is stopped. event loggi ng is stopped when the DS1678 is cleared by writing to the clear enable and memory cl ear bits, or when any memory location including the rtc or control registers is written to during a missi on. the mip bit can also be written to logic zero by the end user to stop event logging via the i 2 c bus. by writing a zero to the mip bit and stopping the mission, a zero is automatically written to the me bit of the control register. it cannot, however, be written to logic one to start a mission unless the me m clr bit is a one to signi fy that the memory has been cleared. bit 4: clear memory (cm). this bit triggers the memory to be cleared if the clr clear enable and eosc oscillator enable bits in the control regist er are set to one. this causes the event-log memory, event counter, and start time stamp registers to a ll be cleared to zeros. once the memory has been cleared, the clr enable bit and the cm bits are set to zeros, and the mem clr bit is set to one to allow a new mission to begin. clearing the memory is a tw o-write process to reduce the risk of accidentally erasing the memory. the clr bit must be set to one be fore the cm bit can be written to one. during the clear memory operation, the DS1678 should not be accessed for 500 p s while the memory is erased. the mem clr bit should read a one before trying to access the cleared memory or registers. bit 3: low-battery flag (lobat). this bit reflects the status of th e backup power source connected to the v bat pin. a logic one for this bit indicates an exhauste d lithium energy source. bit 2: rollover flag (rof). this bit is set to one if the ro bit of the control register is set to one, the last data log memory location has been filled, and a new event has occurred, which causes the time/date stamp to be overwritten. if ro is se t to zero (rollover is disabled), th e last data log memory location has been filled, and a new event has occurred, rof is set to one to indicate that more events have occurred than the number of available memory locations. the ev ent counter continues to record events, even after the event-log memory is full. the rof is cleared by the clear memory command. bit 0: alarm flag (almf). a logic one in the alarm flag bit indi cates that the current time has matched the time-of-day alarm registers. if, at the sa me time, the disx bits are both logic zero, int goes low to issue an alarm interrupt. almf is a read-only bit a nd is cleared by accessing any of the alarm register bytes either with a read or a write. writing any memory location during a mission stops the mission. a mission cannot be started when th e disx bits are set to zero.
DS1678 real-tim e event re corder 2 1 of 25 event counter regi ster (3ah?3ch) this three-byte register set provid es the num ber of events that have been logged during the current data- logging operation (also known as a ?m issi on?). the contents of this regist er can be used by software to point to th e m o st recen t data sam p le in the event- log m e mory. the data in these registers are cleared when the event-log m e mory is cleared. the event counter is not in crem ented when the etc reaches ffffh and rolls over to the next 16 bits of m e m o r y. address pointer re gister (3fh?40h) the address pointe r regis t er a l ways c ontains the a ddre ss tha t the next data lsb is written to in th e event- log m e mory. the address pointer registers are located in th e m a in m e mory m a p at lsb (3fh) and msb (40h). these are helpful in recovering all the data if a rollover occurs. the address pointer points to the oldest even t in the m e m o ry af ter a rollover. th is is the m e m o ry loca tion th at would be overwritten by the next event. read the data f r om this point to the end of the mem o ry and t h e start tim e stam p, including the two-byte et c f r om the last even t to rec over all the data in th e correct o r d e r. glitch- control circui t the DS1678 has a built-in glitch-c ontrol circuit to filter noise on int from triggering false events. a m i ni m u m of one internal clock cycle (0.122m s) up to a m a ximum of two internal clock cycles (0.245m s ) are required to recognize a transition on the input as an event. an event then requires an addition a l six to eight internal clock cycles (0.752m s to 0.977m s) to be processed and recorded into m e mory. this m e ans that the m i nim u m event occurrence that can be r ecognized by the DS1678 requires seven to 10 internal clock cycles (0.854m s to 1.22m s). fa ilure to ensure this tim i ng causes the event to be ignored. thus, it is recomm ended that you design with the m a xi m u m tim ing specs. see figure 5. int has a w eak internal pulldown resist or to prevent the pin from floati ng if the signal connected to the pin is tri-stated. w ithout the resi stor, the input would float and potentially log phantom events. w ith the pulldown re sisto r , the pin can be tra n sition e d to a low state, causing an e v ent to be r e corded if int is held high by an outside signal that becom e s tri-stated. figure 5. e vent recognition timing transiti o n po int transiti o n po int transiti o n po int transiti o n po int transiti o n po int event o n b ot h e dges gli t ch t gli t ch t even t t i nt i nt bad event 2 event 2 is missed event 1 bad event 1 i nt even t t go od e v e nts event 2 event 1 event on rising edge gli t ch t gli t ch t even t t i nt i nt bad event 2 event 2 is missed event 1 transiti o n po int bad event 1 i nt even t t go od e v e nts event 2 event 1
DS1678 real-tim e event re corder 2 2 of 25 security the DS1678 provides several measures to ensure data integrity for the end user. these security measures are intended to prevent third-party intermediaries from tampering with the data that has been stored in the event-log memory. as a first security measure, the event-log memory is read-only from the perspective of the end user. the DS1678 can write the data into these memory banks, but the end user cannot wr ite data to individual registers. this prevents an unscrupulous intermed iary from writing false data to the DS1678. the end user, however, can clear the contents of the even t-log memory. a new mission cannot be started unless the mem clr bit has been set to one to indicat e that the memory and registers are cleared. as a second security measure, changing any value in the memory including the rtc and control registers stops event logging and clears the mip and me bits. the mem clr bit must be set to one so the memory and registers are cleared befo re a new event-log mission can begin. i 2 c serial data bus the DS1678 supports a bidirectional i 2 c bus and data transmission prot ocol. a device that sends data onto the bus is defined as a transmitter, and a device re ceiving data as a receiver . the device that controls the message is called a ?master.? the devices that ar e controlled by the master are ?slaves.? the bus must be controlled by a master device that generates the serial clock (scl), controls the bus access, and generates the start and stop conditions . the DS1678 operates as a slave on the i 2 c bus. connections to the bus are made via the ope n-drain i/o lines sda and scl. the following bus protocol has been defined (figure 6): ? data transfer can be initiate d only when the bus is not busy. ? during data transfer, the da ta line must remain stable whenever the clock line is high. changes in the data line while the clock line is high are interpreted as control signals. accordingly, the following bus conditions have been defined: bus not busy: both data and clock lines remain high. start data transfer: a change in the state of the data line, fr om high to low, while the clock is high, defines a start condition. stop data transfer: a change in the state of the data line, from low to high, while the clock line is high, defines the stop condition. data valid: the state of the data line represents valid data when, after a start condition, the data line is stable for the duration of the high period of the clock signal. the data on the line must be changed during the low period of the clock signal. th ere is one clock pulse per bit of data. each data transfer is initiated with a start condition and terminated with a stop condition. the number of data bytes transferred between start a nd stop conditions is not limited, and is determined by the master device. the information is transfe rred byte-wise and each receiver acknowledges with a ninth bit. within the bu s specifications a standard mode (100kh z clock rate) and a fast mode (400khz clock rate) are defined. the ds 1678 works in both modes. acknowledge: each receiving device, when addressed, is obliged to generate an acknowledge after the reception of each byte. the master devi ce must generate an extra clock puls e which is associated with this acknowledge bit.
DS1678 real-tim e event re corder 2 3 of 25 a device that acknowledges must pull down the sda lin e during the acknowledge clock pulse in such a way that the sda line is stable low during the high period of the acknowledge-r elated clock pulse. of course, setup and hold times must be taken into account. a master must si gnal an end of data to the slave by not generating an acknowledge bit on th e last byte that has been clocked out of the slave. in this case, the slave must leave the data line high to enab le the master to gene rate the stop condition. figure 6 details how data transfer is accomplished on the i 2 c bus. depending upon the state of the r/ w bit, two types of data transfer are possible: 1) data transfer from a master tr ansmitter to a slave receiver. the first byte transmitted by the master is the slave address. next follows a numbe r of data bytes. the slav e returns an acknowledge bit after each received byte. 2) data transfer from a slave tr ansmitter to a master receiver . the first byte (the slave address) is transmitted by the master. the slave then returns an acknowledge bit. next follows a number of data bytes transmitted by the slave to th e master. the master returns an acknowledge bit after all received bytes other than the last byte. at the end of the last received byte, a ?not acknowledge? is returned. the master device generates all the serial clock puls es and the start and stop conditions. a transfer is ended with a stop condition or with a repeated start condition. because a repeated start condition is also the beginning of the next seri al transfer, the bus is not released. the DS1678 can operate in the following two modes: 1) slave receiver mode (DS1678 write mode): serial data and clock are received through sda and scl. after each byte is receive d, the receiver transmits an ac knowledge bit. start and stop conditions are recognized as the beginning and end of a serial transfer. the slave address byte is the first byte received after master generates the star t condition. the address by te contains the 7-bit DS1678 address, which is 1001010, followed by the direction bit (r/ w ), which is 0. the second byte from the master is the register addr ess. this sets the register pointer . if the write is being done to set the register pointer, a stop or repeated start may then be sent by the master. otherwise, the master then transmits each byt e of data, with the DS1678 acknowle dging each byte received. the master generates a stop condition to terminate the data write (figure 7). 2) slave transmitter mode (DS1678 read mode): the first byte is received and handled as in the slave receiver mode. however, in this mode, the direc tion bit indicates that th e transfer direction is reversed. serial data is transm itted on sda by the DS1678 while the serial clock is input on scl. the slave address byte is the first byte received afte r the master generates a start condition. the address byte contains the 7-bit DS1678 address, which is 1001010, followed by the direction bit (r/ w ), which is 1. after receiving a valid slave address byte and di rection bit, the DS1678 generates an acknowledge on the sda line. the DS1678 begins to transmit data on each scl pulse starting with the register address pointed to by the register pointer. as the master reads each byte, it must generate an acknowledge. the DS1678 must receive a ?not acknowledge? on th e last byte to end a read (figure 7).
DS1678 real-tim e event re corder figure 6. data transfer on i 2 c serial bus msb slave address r/w direction bit sda scl start condition 12 6 7 8 9 12 8 9 stop condition or repeated start condition 3 - 8 acknowledgement signal from receiver acknowledgement signal from receiver ack ack repeated if more bytes are transferred figure 7. i 2 c serial communication w i th d s 1678 a2 10 w 0 a 0w 1 s 1 0 a1 a0 00 a a p sd a sc l d e v i c e a d dr es s b y t e m e m o r y a ddr ess b y t e st a r t d s 1678 ac k st o p d s 1678 ack w r i t e t o m e m o r y a d d r ess p o i n t e r 1 s 1 1 0 00 rd a n p sd a sc l d e v i ce a d d r es s b y t e d a ta b y te st a r t d s 1678 ac k st o p ma s t e r na ck r ead s i n g l e b y t e f r o m c u r r e n t m e m o r y a d d r e ss p o i n t e r l o cat i o n d1 d2 d3 d4 d5 d6 d7 0 d0 1 s 1 1 0 d0 00 rd a a sd a sc l d e v i ce a d d r es s b y t e m o s t s i gni f i cant d a ta b y te st a r t d s 1678 ac k ma s t e r ac k r ead m u l t i p l e b y t es f r o m c u r r e n t m e m o r y a d d r ess p o i n t e r l o cat i o n d1 d2 d3 d4 d5 d6 d7 np st o p ma s t e r na ck leas t s i gni f i c ant d a ta b y te d1 d2 d3 d4 d5 d6 d7 0 d0 1 s 1 0 00 a a sd a sc l d e v i ce a d d r es s b y t e m e m o r y a d dr es s b y t e st a r t d s 1678 ac k d s 16 78 ac k r ead s i n g l e b y t e f r o m n e w m e m o r y a d d r ess p o i n t e r l o cat i o n 1 r 1 1 0 00 rd a d e v i ce a ddr ess by t e r epeat ed st a r t d s 1678 ac k np d a ta b y te s t o p ma s t e r na ck d1 d2 d3 d4 d5 d6 d0 sd a sc l d7 sd a sc l w r i t e t o m e m o r y lo c a t i on ( s i ngl e b y t e ) ap st o p d s 1 678 ac k d0 d a ta b y te d1 d2 d3 d4 d5 d6 d7 a3 a4 a5 a6 a7 0w 1 s 1 0 a1 a0 00 a d e v i ce a ddr ess b y t e m e m o r y a ddr es s b y t e st a r t d s 1 678 ac k d s 1678 ac k a2 a3 a4 a5 a6 a7 1 1 a1 a0 a2 a3 a4 a5 a6 a7 2 4 of 25
DS1678 real-time event recorder 25 of 25 maxim/dallas semiconductor cannot assume res ponsibility for use of any circuitry other than circuitry entirely embodied in a ma xim/dallas semiconductor product. no circuit patent licenses are implied. maxi m/dallas semiconductor reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2005 maxim integrated products x printed usa the maxim logo is a registered trademark of maxim integrated products, inc. the dallas logo is a registered trademark of dallas semiconductor corporation. chip information transistor count: 110,836 process: cmos substrate connected to ground thermal information part theta-j a (c/w) theta-j c (c/w) 8 pdip 110 40 8 so 113 31 package information (for the latest package outline information, go to www.maxim-ic.com/dallaspackinfo .) package document number 8-pin plastic dip (300 mils) 56-g5005-000.pdf 8-pin so (208 mils) 56-g4010-001.pdf

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