W83C43 Datasheet, PDF (7/21 Pages) Winbond – KEYBOARD CONTROLLER

W83C43
Status Register (AT Mode), continued
BIT
BIT FUNCTION
2
System Flag
3
Command/data
4
Inhibit Switch
5
Transmit Time-out
6
Receive Time-out
7
Parity Error
DESCRIPTION
This bit may be set to 0 or 1 by writing to the system
flag bit in the command byte of the keyboard controller.
It is set to 0 after a power-on reset
0: Data byte
1: Command byte
0: Keyboard is inhibited
1: Keyboard is not inhibited
0: No transmit time-out error
1: Transmit time-out error
0: No receive time-out error
1: Receive time-out error
0: Odd parity (no error)
1: Even parity (error)
OUTPUT BUFFER
The output buffer is an 8-bit read-only register at I/O address hex 60. The keyboard controller uses
the output buffer to send the scan code received from the keyboard and data bytes required by
commands to the system. The output buffer should be read only when the output buffer full bit in the
register is 1.
ONPUT BUFFER
The input buffer is an 8-bit write-only register at I/O address hex 60 or 64. Writing to address hex 60
sets a flag that indicates a data write; writing to address hex 64 sets a flag that indicates a command
write. Data written to I/O address hex 60 are sent to the keyboard (unless the keyboard controller is
expecting a data byte) following the controller's input buffer only if the input buffer full bit in the status
register is set to 0.
(A) Input Port Definition (AT Mode)
BIT
FUNCTION
0
Undefined
1
Undefined
2
Undefined
3
Undefined
4
RAM on System Board
0: Disable second 256 KB of system board RAM
1: Enable second 256 KB of system board RAM
Publication Release Date: January 1996
-7-
Revision A2