Keyboard

C.2.5 Keyboard Commands

Table C-1 lists the commands that the keyboard can send to the system (specifically, to the 8042-type logic).

Table C-1.Keyboard-to-System Commands
CommandValue

Description

 

 

 

Key Detection Error/Over/run

00h [1]

Indicates to the system that a switch closure

 

FFh [2]

couldn’t be identified.

 

 

 

BAT Completion

AAh

Indicates to the system that the BAT has been

 

 

successful.

 

 

 

BAT Failure

FCh

Indicates failure of the BAT by the keyboard.

 

 

 

Echo

EEh

Indicates that the Echo command was received by

 

 

the keyboard.

 

 

 

Acknowledge (ACK)

FAh

Issued by the keyboard as a response to valid

 

 

system inputs (except the Echo and Resend

 

 

commands).

 

 

 

Resend

FEh

Issued by the keyboard following an invalid

 

 

input.

 

 

 

Keyboard ID

83ABh

Upon receipt of the Read ID command from the

 

 

system, the keyboard issues the ACK command

 

 

followed by the two IDS bytes.

Note:

[1]Modes 2 and 3.

[2]Mode 1 only.

 

C-10

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