VT8235 datasheet(44/145 Pages) VIA

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VT8235 V-Link South Bridge

Revision 1.22 October 24, 2002

-38-

Legacy I/O Registers

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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.

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