Keyboard Technical Information [PC98]


Type Separated
LSI Main board: uPD8251A
Keyboard: uPD8048
Data Lines 6 lines: GND, +5V, Data lines, 3 Control lines
Data Transfer Asynchronous serial communication
Speed: 19,2Kbps
Length: 8 bits
Start bit: 1
Stop bit: 1
Parity bit; Odd
Level: TTL
Data Causing Key-down causes Make data. Key-up causes Break data.
Pressing a key over 0.5 seconds, keyboard repeats Break/Make data.
The order of key data is not specified.


Pin Name
1 !RST
3 !RDY
5 !RTY
6 NC
7 NC
8 +5V

I/O Port

I/O address Descriptions
00xx0100A01 Keyboard Interface uPD8251A
A0 Input operation (Read)
0 8251A Data Read
1 8251A Status Read
Data Read Format
D7 D6 D5 D4 D3 D2 D1 D0
Break/!Make Key Code
Status Read Format
D7 -  
D6 -  
D5 FE Framing Error
D4 OE Overrun Error
D3 PE Parity Error
D2 -  
D1 RxRDY =Pin !RDY
D0 -  
A0 Output operation (Write)
0 8251A Data Write
1 8251A Mode/Command Write
Mode Instruction Format
D7 D6 D5 D4 D3 D2 D1 D0
0 1 0 1 1 1 1 0
Command Instruction Format
D7   Not used
D6 IR Request Internal Reset
D5 KBDE(RTS) KB Send Disable
D4 ER Error Reset
D3 RST(SBRR) Reset
D2 RxE Receiver Enable
D1 RTY(DTR) Retry
D0 TxEN Transmitter Enable

Flow chart


Image: Flow chart of resetting keyboard PC98

Read data

Image: Flow chart of reading key data PC98

inserted by FC2 system