1
NT6881
USB Keyboard Micro-Controller
V2.8
NT6881
2003/2/24 2 Ver2.8
1 REVISION
HISTORY ...................................................................................................................... 4
2 FEATURES
.................................................................................................................................... 5
3 GENERAL
DESCRIPTION ............................................................................................................. 5
4 PIN
CONFIGURATION ................................................................................................................... 5
5 PAD
CONFIGURATION.................................................................................................................. 6
6 BLOCK
DIAGRAM ......................................................................................................................... 7
7 PIN AND PAD DESCRIPTIONS ..................................................................................................... 8
8 FUNCTIONAL
DESCRIPTION
....................................................................................................... 9
8.1 6502CPU ............................................................................................................................... 9
8.2 INSTRUCTION SET LIST .................................................................................................... 10
8.3 MASK ROM ......................................................................................................................... 12
8.4 SRAM .................................................................................................................................. 12
8.5 SYSTEM RESERVED REGISTERS .................................................................................... 13
8.6 POWER-ON RESET ............................................................................................................ 13
8.7 TIMING GENERATOR......................................................................................................... 13
8.8 BASE TIMER (BT) ............................................................................................................... 14
8.9 INTERRUPT CONTROLLER ............................................................................................... 15
8.9.1 TIMER INTERRUPT ............................................................................................................ 15
8.9.2 INT0 INTERRUPT ............................................................................................................... 15
8.9.3 INT1 INTERRUPT ............................................................................................................... 15
8.9.4 KBD INTERRUPT ............................................................................................................... 15
8.9.5 IN0 TOKEN INTERRUPT .................................................................................................... 15
8.9.6 OT0 (OUT0) TOKEN INTERRUPT ...................................................................................... 15
8.9.7 IN1 TOKEN INTERRUPT .................................................................................................... 16
8.9.8 IN2 TOKEN INTERRUPT .................................................................................................... 16
NT6881
2003/2/24 3 Ver2.8
8.9.9 STUP (SETUP) TOKEN INTERRUPT ................................................................................. 16
8.9.10 SUSP INTERRUPT............................................................................................................ 16
8.10 I/O PORTS ......................................................................................................................... 16
8.11 WATCH-DOG TIMER (WDT).............................................................................................. 17
8.12 POWER CONTROL ........................................................................................................... 17
8.13 UNIVERSAL SERIAL BUS INTERFACE............................................................................ 17
8.14 SUSPEND AND RESUME.................................................................................................. 17
8.15 RESET SOURCE SUMMERY ............................................................................................ 18
8.16 PS/2 MOUSE APPLICATION............................................................................................. 18
9 ABSOLUTE
MAXIMUM
RATING.................................................................................................. 19
10 DC ELECTRICAL CHARACTERISTICS ....................................................................................... 19
11 AC ELECTRICAL CHARACTERISTICS ....................................................................................... 20
12 APPLICATION CIRCUIT 1 (SIMPLE KEYBOARD WITH PS/2 MOUSE) ..................................... 21
13 APPLICATION CIRCUIT 2 (WINDOWS 2000 COMPATIBLE KEYBOARD) ................................ 22
14 APPLICATION CIRCUIT 3 (MINI KEYBOARD)............................................................................ 23
11 BONDING DIAGRAM ................................................................................................................... 25
12 ORDERING INFORMATION ........................................................................................................ 26
13 PACKAGE INFORMATION ......................................................................................................... 27
NT6881
2003/2/24 4 Ver2.8
Revision History
NT6881 Specification Revision History
Version Content Data
2.8
1. Application circuit 1, 2 and 3 add 0.1uF to
RESET
(Page
21, 22 and 23)
2. Code number modified (Page 26)
Feb. 2003
2.7
1. FN Key Model Usage for Consumer Keys modified -
FN_K22 and FN_K24 (Page 19)
Oct. 2002
2.6
1. Volume Knob Application deleted (Page 13)
2. PS/2 Mouse Application added (Page 13 and 14)
3. Application circuit 2 and 3 modified (Page 17 and 18)
4. FN key usage added (Page 19)
5. Standard code functional descriptions modified (Page 21)
Sep. 2002
2.5
1. Application circuits modified (Page 15, 16 and 17)
2. Standard code functional description added (Page19)
July 2002
1.0
Original
Nov. 1998
NT6881
2003/2/24 5 Ver2.8
Features
!
Built-in
6502
8-bit CPU
!
3 MHz CPU operation frequency when oscillator is running at 6 MHz
!
6K bytes of ROM
! 256 bytes of SRAM
!
One 8-bit programmable base timer with pre-divider circuit
!
29 programmable bi-directional I/O pins including two external interrupts
!
3 LED direct sink pins with internal serial resistors
!
On-chip oscillator (Crystal or Ceramic Resonator)
!
Watch-dog timer reset
!
Built-in power on reset
!
USB interface
!
3 Endpoints provided
!
Remote Wakeup provided
!
CMOS technology for low power consumption
!
40-pin DIP package, 42-pad Chip Form and COB
General Description
The NT6881 is a single chip micro-controller for USB keyboard applications. It incorporates a 6502 8-bit CPU core, 6K bytes
of mask ROM, and 256 bytes of RAM used as working RAM and stack area. It also includes 29 programmable bi-directional
I/O pins with built-in resistors, and one 8-bit pre-loadable base timer. Additionally, it includes a built-in power-on reset, a
built-in low voltage reset, an oscillator that requires crystal or ceramic resonator applied, and a watch-dog timer that
prevents system standstill.
Pin Configuration
GND
VCP
VDP
VDM
P30
P31
INT0/P32
INT1/P33
P34
P11
P00
P02
P03
P17
P04
P20
P21
P22
P23
P25
P26
LED0
LED1
V
DD
LED2
OSCO
OSCI
P12
P27
N
T
6881
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
RESET
P01
P05
P06
P07
P10
17
18
19
20
P24
P16
P15
P14
P13
24
23
22
21
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