VT82C596 datasheet(37/96 Pages) ETC

37 / 96 page

VT82C596B

Revision 0.3 June 17, 1999

-31-

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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

the

VT82C596B are listed n the table below.

Note: The VT82C596B Keyboard Controller is compatible

with

the

VIA

VT82C42

Industry-Standard

Keyboard

Controller except that due to its integrated nature, many of the

input and output port pins are not available externally for use

as general purpose I/O pins (even though P13-P16 are set on

power-up as strapping options). In other words, many of the

commands below are provided and “work”, but otherwise

perform no useful function (e.g., commands that set P12-P17

high or low). Also note that setting P10-11, P22-23, P26-27,

and T0-1 high or low directly serves no useful purpose, since

these bits are used to implement the keyboard and mouse ports

and are directly controlled by keyboard controller logic.

Table 4. 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)

9xh

Write low nibble (bits 0-3) to P10-P13

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 #

B0h

Set P10 low

B1h

Set P11 low

B2h

Set P12 low

B3h

Set P13 low

B4h

Set P22 low

B5h

Set P23 low

B6h

Set P14 low

B7h

Set P15 low

B8h

Set P10 high

B9h

Set P11 high

BAh

Set P12 high

BBh

Set P13 high

BCh

Set P22 high

BDh

Set P23 high

BEh

Set P14 high

BFh

Set P15 high

Code

Keyboard Command Code Description

C0h

Read input port (read P10-17 input data to

the output buffer)

C1h

Poll input port low (read input data on P11-13

repeatably & put in bits 5-7 of status

C2h

Poll input port high (same except P15-17)

C8h

Unblock P22-23 (use before D1 to change

active mode)

C9h

Reblock P22-23 (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 P10-17 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 test inputs (T0-1 read to bits 0-1 of resp byte)

Exh

Set P23-P21 per command bits 3-1

Fxh

Pulse P23-P20 low for 6usec per command bits 3-0

All other codes not listed are undefined.

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