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NT6868C
Keyboard Controller
Features
n n n n n Built-in 6502 8-bit CPU 2 MHz CPU operation frequency 4K bytes of ROM 128 bytes of SRAM One 8-bit programmable base timer with 1 - 256 sec interval n 29 programmable bi-directional I/O pins n 3 LED direct sink pins with internal serial resistors n Mask optional for built-in RC oscillator with an external resistor or external ceramic resonator applied n Mask optional for DATA/CLK driving capability n Watch-dog timer n Built-in power-on reset n Built-in low voltage reset n CMOS technology for low power consumption n Available in 40 pin DIP package and 40 pad CHIP FORM
General Description
NT6868C is a single chip micro-controller for keyboard applications. It incorporates a 6502 8-bit CPU core, 4K bytes of ROM and 128 bytes of RAM used as working RAM and stack area. It also includes 29 programmable bi-directional I/O pins and one 8-bit pre-loadable base timer. Additionally, it includes a built-in low voltage reset, a 4MHz RC oscillator that only requires an externally applied or a 4MHz ceramic resonator, and a watch-dog timer that has a resistor preventing system standstill.
Pin Configuration
Pad Configuration
P 1 7 P 1 6 P 1 5 P 1 4 P 1 3 P 1 2 P 1 1 P 1 0 P 0 7 P 0 6
GND NC DATA CLK P30 P31 P32 P33 P34 RESET P00 P01 P02 P03 P04 P05 P06 P07 P10 P11
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21
OSCI R/OSCO VDD LED2 LED1 LED0 P27 P26 P25 P24 P23 P22 P21 P20 P17 P16 P15 P14 P13 P12
26
25
24
23
22
21
20
19
18
17
16 15
P05 P04 P03 P02 P01 P00 RESET P34 P33 P32
P20 P21 P22 P23 P24 P25 P26 P27 LED0 LED1
27 28 29 30 31 32 33 34 35 36 37 38 39 40 1 2 3 4 5
14 13 12 11 10 9 8 7
NT6868C
NT6868CH
6
P31
L E D 2
V
D D
R / O S C O
O S C I
G N D
N C
D A T A
C L K
P 3 0
1
V2.0
NT6868C
Block Diagram
CLK TIMING GENERATOR (RC OSC/Ceramic Resonator: 4MHz) 4K BYTES ROM
DATA
LED0
LED1
6502 CPU
128 BYTES SRAM + STACK
LED2
I/O PORTS
P00 - P07
INT. CONTROLLER
WATCH DOG TIMER
P10 - P17
P20 - P27 RESET VDD GND POWER-ON RESET/ LOW VOLTAGE RESET BASE TIMER P30 - P34
Pin and Pad Descriptions
Pin No. 1 2 3 4 5 - 9, 11 - 34 10 35 - 37 38 39 40 Pad No. 1 2 3 4 5 - 9, 11 - 34 10 35 - 37 38 39 40 Designation GND NC DATA CLK P30 - P34, P00 - P27 RESET LED0 LED2 VDD R/OSCO OSCI I/O P I/O I/O I/O I O P I Ground pin No connection, recommended to connect VDD or floating I/O, 10K pull-up resistor for communication I/O, 10K pull-up resistor for communication Bi-directional I/O pins RESET signal input pin with internal pull-up resistor; Active low LED direct sink pins Power supply 47K resistor connected for RC OSC or 4MHz ceramic resonator connection No connection for RC OSC connection; for 4MHz ceramic resonator Description
* Under the constraint of the maximum frequency variation, (F/F)max, 1%, code 3, 7 (ceramic resonator option) must be selected while pins 39 and 40 are connected to a ceramic resonator. If (F/F)max, 10%, code 1, 5 (RC OSC option), then it is recommended to be selected. Also, connect pin 39 a 47K resistor with, 1% accuracy to VDD while pin 40 is floating.
2
NT6868C
Functional Description
6502 CPU 6502 is an 8-bit CPU. Please refer to 6502 data sheet for more details.
7 ACCUMULATOR A 7 INDEX REGISTER X
0 0000 SRAM 0 009F UNUSED 00C0 0 INDEX REGISTER Y SYSTEM REGISTERS 00CF STACK PTR
7
15 PROGRAM COUNTER PC 7 S 7 S V B D I Z
0
UNUSED
0 STACK POINTER SP 0 C STATUS REGISTER P
EC00
USER ROM
FFFA CARRY FFFB ZERO INTERRUPT MASK DECIMAL MODE BREAK OVERFOLW SIGN FFFC RST-L FFFD RST-H FFFE IRQ-L FFFF IRQ-H IRQ VECTOR NMI-H NMI-L NMI VECTOR
Figure 1. 6502 CPU Registers and Status Flags
Figure 2. NT6868C Memory Map
3
NT6868C
System Reserved Registers
Address $00C0 $00C1 $00C2 $00C3 $00C4 $00C5 $00C6 $00C7 $00C8 $00C9 $00CA $00CB $00CC $00CD $00CE $00CF - : no effect Register BT TCON CLRIRQX PORT0 PORT1 PORT2 PORT3 CLK DATA LED CLRWDT X X X X X Bit7 BT7 PD07 PD17 PD27 0 X X X X X Bit6 BT6 PD06 PD16 PD26 1 X X X X X Bit5 BT5 PD05 PD15 PD25 0 X X X X X Bit4 BT4 PD04 PD14 PD24 PD34 1 X X X X X Bit3 BT3 PD03 PD13 PD23 PD33 0 X X X X X Bit2 BT2 PD02 PD12 PD22 PD32 LED2 1 X X X X X Bit1 BT1 PD01 PD11 PD21 PD31 LED1 0 X X X X X Bit0 BT0 ENBT CLRIRQTMR PD00 PD10 PD20 PD30 CLK DATA LED0 1 X X X X X R/W W W W RW RW RW RW RW RW W W X X X X X
X : access not allowed
4K X 8 ROM
The built-in ROM program code, executed by the 6502 CPU, has a capacity of 4K X 8 bits and is addressed from F000H to FFFFH.
Power-On Reset
The built-in power-on reset circuit can generate a 150ms pulse to reset the entire chip. The beginning of the 150ms pulse occurs at 60% of VDD when powered on.
128 X 8 SRAM
The built-in SRAM is used for general purpose data memory and for the stack area. SRAM is addressed from 0000H to 007FH. The user can allocate stack area in the SRAM by setting the stack pointer register (S). Since 6502C's default stack pointer is 01FFH, it must be mapped to 007FH. Mapping from 01XX to 00XX is done internally by setting the S register to 7FH via software programming. For example : LDX TXS #$7F
power VDD 60% The start of 150ms pulse t
4
NT6868C
Timing Generation
This block generates the system timing and control signal supplied to the CPU and on-chip peripherals. There are two types of system clock sources: a built-in RC oscillator or an external ceramic resonator. Both of them are mask optional and generate a 4MHz system clock. They also generate 2MHz for the CPU, and 1 MHz for the base timer. The following shows the relationship of code type number with oscillation type. Oscillator RC OSC External Resistor Code Number 1, 5 3, 7 The following table provides the relationship between the external resistor and the RC OSC frequency. (This is for reference only) External Resistor (K ) 39 43 47 56 RC OSC Frequency (MHz) 4.7 4.44 4 3.68
Base Timer
The base timer is an 8-bit counter with a 1MHz clock source. The base timer can be enabled/disabled by the CPU. After a reset, the base timer is disabled and cleared. The base timer can be preset by writing BT7 - BT0 to the BT register at any time. When enabled, the base timer starts counting from the preset value. When the value reaches FFH, it generates a timer interrupt only if the timer interrupt is enabled. When it reaches the maximum value of FFH, the base timer will wrap around and begin counting at 00H. The timer interval can be programmed from 1 - 256 sec. The base timer can be enabled by writing a '0' to ' ENBT ' in the TCON (Timer Control) register. The ENBT is a level trigger. Base timer structure: 8-Bit timer 1s BT Pre-loaded Data: Addr. $00C0 Timer Control Register: $00C1 TCON ENBT (W) Bit BT 7 BT7 6 BT6 5 BT5 4 BT4 3 BT3 2 BT2 1 BT1 0 BT0 R/W (W) BT7 BT6 BT5 BT4 BT2 BT2 BT1 BT0 TMRINT
INT. Controller
When a BASE TIMER overflow occurs, it will set the IRQTMR flag. The IRQTMR flag cannot be directly accessed by the software. Once set by an interrupt source, it remains HIGH unless cleared by writing '1' to the corresponding bit in CLRIRQX ($00C2H). This register is cleared to '0' on initialization by a system reset. When an interrupt occurs, the CPU will jump to $FFFEH & $FFFFH to execute the interrupt service routine. When a BASE TIMER interrupt occurs and enters the interrupt service routine, the IRQTMR flag must be cleared by the software. Interrupt Control Register: Addr. $00C2 Bit CLRIRQX 7 6 5 4 3 2 1 0 CLRIRQTMR R/W (W)
5
NT6868C
I/O Ports
The NT6868C has 31 pins dedicated to input and output. These pins are grouped into 6 ports as follows:
PORT 0 (P00 - P07):
Port 0 is an 8-bit bi-directional CMOS I/O port that is internally pulled HIGH by PMOS. Each pin of port 0 can be bit programmed as an input or output pin under the software control. When programmed as output, data is latched to the port data register and output to the pin. Port 0 pins with ''1'' written to them are pulled HIGH by the internal PMOS pull-ups, and are used as input in that state. These input signals can then be read. The port output will be HIGH after reset. PORT 1 ( P10 - P17 ) : These functions are the same as PORT 0. PORT 2 ( P20 - P27) PORT 3 ( P30 - P34) CLK & DATA PORT Registers: Addr. $00C3 $00C4 $00C5 $00C6 $00C7 $00C8 Bit PORT0 PORT1 PORT2 PORT3 CLK DATA 7 PD07 PD17 PD27 6 PD06 PD16 PD26 5 PD05 PD15 PD25 4 PD04 PD14 PD24 PD34 3 PD03 PD13 PD23 PD33 2 PD02 PD12 PD22 PD32 1 PD01 PD11 PD21 PD31 0 PD00 PD10 PD20 PD30 CLK DATA R/W (RW) (RW) (RW) (RW) (RW) (RW) : These functions s are the same as PORT 0. : These functions are the same as PORT 0. : These two pins have the same structure as I/O ports.
VDD Latch WREN L Q DB D RST SD IO Weak PMOS
RDENB
IO Port Structure
6
NT6868C
LED Port
There are 3 LED direct sink pins which require no external serial resistors. The address is mapped to address $00C9. Addr. $00C9 Bit LED 7 6 5 4 3 2 LED2 1 LED1 0 LED0 R/W (W)
WREN L Q DB D RST SD
LED [ 0 ]
VDD WREN L Q DB D RST SD LED [ 1:2 ]
LED0 Port Structure
LED1, LED2 Port Structures
Watch-Dog Timer
NT6868C implements a watch-dog timer, which protects programs against system standstill. The clock of the watch-dog timer is derived from the on-chip RC oscillator. The watch-dog timer interval is about 0.175 of a second. The timer must be cleared within every 0.175 second during normal operation; otherwise, it will overflow and cause a system reset. The watch-dog timer is cleared and enabled after a system reset. It cannot be disabled by the software. The user can clear the watch-dog timer by writing #55H to CLRWDT ($00CAH) register. For example: LDA STA Addr. $00CA Bit CLRWDT
#$55 $00CA 7 0 6 1 5 0 4 1 3 0 2 1 1 0 0 1 R/W (W)
Low Voltage Reset (LVR) Circuit
The NT6868C will check on the voltage level of the power supply. When the voltage level of power supply is below a threshold of 3.0V (Typical), the LVRC will issue a reset output to the chip until the power voltage level is above a threshold voltage of 3.0V (Typical) again. As soon as the power voltage reaches 3.0V (Typical), the entire chip will be reset for about 150ms.
RESET NT6868C can also be externally reset through the RESET pin. A reset is initiated when the signal at the RESET pin is held LOW for at least 10 system clocks. As soon as the RESET signal goes high, the NT6868C begins to reset for about 150ms. The following shows the definition of the RESET input at LOW pulse width.
VDD VDD
20%VDD Trstb
20%VDD
7
NT6868C
Absolute Maximum Ratings*
DC Supply Voltage . . . . . . . . . . . . . . -0.3V to +7.0V Input/Output Voltage . . . . . . GND -0.2V to VD D + 0.2V Operating Ambient Temperature . . . . . . 0 C to +70C Storage Temperature . . . . . . . . . . . . . -55C to +125C Operating Voltage (VD D ) . . . . . . . . . .+4.5V to 5.5V
*Comments
Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to this device. These are stress ratings only. Functional operation of this device at these or any other conditions above those indicated in the operational sections of this specification is not implied or intended. Exposure to the absolute maximum rating conditions for extended periods may affect device reliability.
DC Electrical Characteristics (VDD = 5V, GND = 0V, TA = 25C, FOSC = 4MHz, unless otherwise specified)
Symbol ICC VIH VIL VOH1 VOH2 VOH3 VOL1 VOL2 VOL3 F/F F/F Parameter Power Supply Current Input High Voltage Input Low Voltage Output High Voltage (Port 0, 1, 2, 3) Output High Voltage (CLK, DATA) Output High Voltage (CLK, DATA) Output Low Voltage (PORT 0, 1, 2) Output Low Voltage (PORT 3) Output Low Voltage (CLK, DATA) Initial Frequency Variation 1 2.4 2.4 2.4 0.4 0.4 0.4 +/-10 2 0.8 Min. Typ. Max. 20 Unit mA V V V V V V V V % IOH = -100A IOH = -400A, Note 1 IOH = -800A, Note 2 IOL = 4mA IOL = 5mA IOL = 10mA For RC OSC option only; By Lots For ceramic resonator option only; By Lots VOL = 3.2V Conditions No load
Frequency Variation 2
+/-1
%
ILED VLVR TPOR TRSTB RPH
LED Sink Current (LED 0, 1, 2) Low Voltage Reset Threshold Power-on Reset Time RESET Input Low Pulse Width RESET Pull High Resistor
10
14 3.0
17
mA V
120 2.5
150
180
ms s 10 system clocks
220
K
Note 1: There are 2 types of DATA/CLK driving capabilities. This condition of VOH2 is the same as the specification of NT6868A. Under this condition, the user can select mask option 1 or 3. Note 2: The driving capability of DATA/CLK is higher than V OH2. Under this condition, the user can select mask option 5 or 7.
8
NT6868C
Application Circuit I (for reference only)
VDD
4.7 - 10 mf
P00 P01 P02 P03 P04 P05 P06 P07 P10 P11 P12 P13 P14 P15 P16 P17 P30 P31
VDD
VDD GND Scroll Lock LED0 Num Lock LED1 Caps Lock LED2 0.1mf RESET Optional
NT6868C
DATA CLK KBD DATA KBD CLOCK VDD R/OSCO 47K (System clock can be decreased by increasing the resistance)
P20 P21 P22 P23 P24 P25 P26 P27
R0 S0 S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 9 S13 S14 S15 S16 S17 PgUp + Pause Q W E R U I O P Scroll Lock K14 7 Home 8
R1
R2
R3
R4 (R) Ctrl
R5
R6 (L) Ctrl
R7
F5 ! 1 @ 2 # 3 $ 4 & 7 * 8 ( 9 ) 0 Print Screen
Tab Caps Lock F3 T Y } ] F7 { [
A S D F J K L : ;
Esc (K45) Macro F4 G H F6
Z X C V M < , > .
K131 K132 K133 B N K56 APP ? / (R) Alt
~ , F1 F2 % 5 ^ 6 + = F8 -
" ' (L) Alt
| \(K42)
Back Space 4 5 6
| \(K29) 1 End 2 3 PgDn (R)
F11 Space 0 Ins . Del
Enter Num Lock / *
F12
F9 Delete Insert
F10
-
Page Up Home
Page Down End
K107 (L) Shift WINL
Enter (R) Shift
WINR
9
NT6868C
Application Circuit II (for reference only)
VDD
4.7 - 10f VDD P00 VDD P01 P02 P03 P04 P05 P06 P07 P10 P11 P12 P13 P14 P15 P16 P17 P30 NT6868C P31 GND Scroll Lock LED0 Num Lock LED1 Caps Lock LED2 0.1f RESET Optional
DATA CLK P20 P21 P22 P23 P24 P25 P26 P27
KBD DATA KBD CLOCK
R/OSCO
4MHz Ceramic Resonator
OSCI
R0 S0 S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 9 PgUp + Pause Q W E R U I O P Scroll Lock K14 7 Home 8
R1
R2
R3
R4 (R) Ctrl
R5
R6 (L) Ctrl
R7
F5 ! 1 @ 2 # 3 $ 4 & 7 * 8 ( 9 ) 0 Print Screen
Tab Caps Lock F3 T Y } ] F7 { [
A S D F J K L : ;
Esc (K45) Macro F4 G H F6
Z X C V M < , > .
K131 K132 K133 B N K56 APP ? / (R) Alt
~ , F1 F2 % 5 ^ 6 + = F8 -
" ' (L) Alt
| \(K42)
Back Space 4 5 6
| \(K29) 1 End 2 3 PgDn (R) Enter (R) Shift F11 Space 0 Ins . Del * / Enter Num Lock F12 F9 Delete Insert Page Up Home Page Down End F10
K107 (L) Shift WINL
WINR
10
NT6868C
Application Circuit For Windows 2000 Standard Code
47K
S0 S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18
P15 P30 P31 P00 P01 P02 P03 P04 P13 P14 P12 P10 P07 P06 P05 P11 P16 P17 P32
R_OSC Scroll Lock LED 0 Num Lock LED 1 Caps Lock LED 2
.1uF
NT6868A/C
VDD VDD
10uF
GND
GND
R0 R1 R2 R3 R4 R5 R6 R7
P20 P21 P22 P23 P24 P25 P26 P27 RESET 10
0.1uF
DATA
DATA
CLOCK CLOCK
11
NT6868C
Key Matrix definition for Windows 2000 Standard Code
Pause
126
Power
163
Sleep
164
R-Ctrl
64
Wake Up
165 58
L-Ctrl
116
F5
S0
Q
17 16
Tab
31
A
110
Esc
46
Z
(K131)
131 1
~
F1
!
2
1 @
S1
W
18
Caps Lock
30 32
S
(K45)
45 47
X
(K132)
132 112
3
2 #
S2
E
19 114
F3
33
D
115
F4
48
C
(K133)
133 113
F2
4
3 $ 4 &
S3
R
20 21
T
34
F
35
G
49
V
50
B
6
% 5 ^
7 5
S4
U
23 22
Y
37
J
36
H
52
M
51
N
6 +
8
7 *
S5
I
24 28
} ] F7
118 39 38
K
117
F6
53
< , >
54 56
(K56)
13
= F8
9
8 (
S6
O
25
L
App
162 119
. |
10
9 )
S7
P
26 27
{ [
40
: ;
41
" ' L-Alt
60 42
?
55
_
12
\
/ R-Alt
-
11
0
S8
Scroll Lock
125
62
Print 124Screen
S9
(K14)
14
Back Space
15 29
| \ (101) 122 1
F11
43
Enter
123
F12
120
F9
121
F10
S10
7
91 (Home) 92 (
4
) 93
Space
61
Num Lock
90 84
Delete
76
Power
163
(End)
S11
8
96 ( ) 97
5
(Num) 98 (
2
) 99
0
(Ins) 95
/
(Num) 89 75
Insert
Sleep
164
S12
9
101 (Page Up) 102 (
6
)
3
103 (Page Dn) 104
.
(Del)
*
100 (Num)
105 (Num)
Page Up
85
Page Down
86
S13
+
106 (Num)
(K107)
107
Enter
108 (Num) 83 Media Previous 181 WWW Search 188 WWW Stop 192 My Computer 197
Media 180 Next
Media Stop 182 WWW Home 189 WWW Refresh 193
Home
79 Media Play 183 80 Media Mute 184 81
End
S14
Wake Up
165
L-Shift
44
R-Shift
57 WWW Mail 187
Volume +
185
S15
Volume 186
L-Win
160 WWW Forward 191 Media Select 195
WWW Back 190 WWW Bookmark 194
S16
Kor_L
134
R-Win
161
Kor_R
135
S17
Calculator
196
S18 R4 R5 R6 R7
R0
R1
R2
R3
12
NT6868C
Bonding Diagram
P 1 7 P 1 6 P 1 5 P 1 4 P 1 3 P 1 2 P 1 1 P 1 0 P 0 7 P 0 6
26
25
24
23
22
21
20
19
18
17
16 15
P05 P04 P03 P02 P01 P00 RESET P34 P33 P32
P20 P21 P22 P23 P24 P25 P26 P27 LED0 LED1
27 28 29 30 31 32 33 34 35 36 37 38 39
NT6868CH
Y
14 13 12 11 X 10 9 8 7
(0, 0)
1752.6 m
40
1
2
3
4
5
6
P31
L E D 2
V
D D
R / O S C O
O S C I
G N D
N C
D A T A
C L K
P 3 0
1930.4 m
*Substrate Connect to Gnd unit: m Pad No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Designation GND NC DATA CLK P30 P31 P32 P33 P34 RESET P00 P01 P02 P03 P04 P05 P06 P07 P10 P11 X -26.70 103.30 233.30 497.55 623.30 752.55 765.20 765.20 765.20 765.20 765.20 765.20 765.20 765.20 765.20 765.20 537.50 407.50 277.50 147.50 Y -680.90 -743.05 -735.35 -743.05 -735.35 -735.95 -447.35 -317.35 -187.35 -57.35 72.65 202.65 332.65 462.65 592.65 735.15 734.15 734.15 734.15 734.15 Pad No. 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Designation P12 P13 P14 P15 P16 P17 P20 P21 P22 P23 P24 P25 P26 P27 LED0 LED1 LED2 VDD R/OSCO OSCI X 17.50 -112.50 -242.50 -372.50 -502.50 -645.00 -765.55 -765.55 -765.55 -765.55 -765.55 -765.55 -765.55 -765.55 -765.55 -765.55 -546.70 -416.70 -286.70 -156.70 Y 734.15 734.15 734.15 734.15 734.15 734.15 576.30 434.30 304.30 174.15 44.00 -86.00 -216.00 -346.00 -476.00 -622.10 -632.30 -617.30 -617.30 -617.30
13
NT6868C
Ordering Information
Part No. NT6868CH NT6868C Package CHIP FORM 40L DIP
Code Type No. 1XXXX 3XXXX 5XXXX 7XXXX
Oscillation Type Built-in RC OSC Ceramic Resonator Built-in RC OSC Ceramic Resonator
Data/Clk Driving capacitance V OH2 V OH2 V OH3 V OH3
14
NT6868C
Package Information
DIP 40L Outline Dimensions unit: inches/mm
D 40 21
E1
1 S
20 E C
A2
A
A1
Base Plane
Seating Plane B B1 e1 eA
L
Symbol A A1 A2 B
Dimensions in inches 0.210 Max. 0.010 Min. 0.1550.010 0.018 +0.004 -0.002 0.050 +0.004 -0.002 0.010 +0.004 -0.002 2.055 Typ. (2.075 Max.) 0.6000.010 0.550 Typ. (0.562 Max.) 0.1000.010 0.1300.010 0 ~ 15 0.6550.035 0.093 Max.
Dimensions in mm 5.33 Max. 0.25 Min. 3.940.25 0.46 +0.10 -0.05 1.27 +0.10 -0.05 0.25 +0.10 -0.05 52.20 Typ. (52.71 Max.) 15.240.25 13.97 Typ. (14.27 Max.) 2.540.25 3.300.25 0 ~ 15 16.640.89 2.36 Max.
B1
C
D E E1 e1 L eA S
Notes: 1. The maximum value of dimension D includes end flash. 2. Dimension E1 does not include resin fins. 3. Dimension S includes end flash.
15

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