Product specifications

VT8235 V-Link South Bridge
Revision 1.22 October 24, 2002 -38- Legacy I/O Registers
Port 64 - Keyboard / Mouse Command.......................... WO
This port is used to send commands to the keyboard / mouse
controller. The command codes recognized by the VT8235
are listed in the table below.
Table 8. Keyboard Controller Command Codes
Code Keyboard Command Code Description
20h Read Control Byte (next byte is Control Byte)
21-3Fh Read SRAM Data (next byte is Data Byte)
60h Write Control Byte (next byte is Control Byte)
61-7Fh Write SRAM Data (next byte is Data Byte)
A1h Output Keyboard Controller Version #
A4h Test if Password is installed
(always returns F1h to indicate not installed)
A7h Disable Mouse Interface
A8h Enable Mouse Interface
A9h Mouse Interface Test (puts test results in port 60h)
(value: 0=OK, 1=clk stuck low, 2=clk stuck high,
3=data stuck lo, 4=data stuck hi, FF=general error)
AAh KBC self test (returns 55h if OK, FCh if not)
ABh Keyboard Interface Test (see A9h Mouse Test)
ADh Disable Keyboard Interface
AEh Enable Keyboard Interface
AFh Return Version #
C0h Read Input Port (read input data to output buffer)
C1h Poll Input Port (read Mouse Data In
continuously to status bit 5
C8h Unblock Mouse Output (use before D1 to change
active mode)
C9h Reblock Mouse Output (protection mechanism
for D1)
CAh Read Mode (output KBC mode info to port 60
output buffer: bit-0=0 if ISA, 1 if PS/2)
D0h Read Output Port (copy output port values
to port 60)
D1h Write Output Port (data byte following is written to
keyboard output port as if it came from keyboard)
D2h Write Keyboard Output Buffer & clear status bit-5
(write following byte to keyboard)
D3h Write Mouse Output Buffer & set status bit-5 (write
following byte to mouse; put value in mouse input
buffer so it appears to have come from the mouse)
D4h Write Mouse (write following byte to mouse)
E0h Read Keyboard Clock In and Mouse Clock In
(return in bits 0-1 respectively of response byte)
Exh Set Mouse Clock Out per command bit 3
Set Mouse Data Out per command bit 2
Set Gate A20 per command bit 1
Fxh Pulse Mouse Clock Out low for 6usec per cmd bit 3
Pulse Mouse Data Out low for 6usec per cmd bit 2
Pulse Gate A20 low for 6usec per command bit 1
Pulse System Reset low for 6usec per cmd bit 0
All other codes not listed are undefined.