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Technical Reference Guide
C.2.5 KEYBOARD COMMANDS
Table
Table
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| Table |
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Command | Value | Description |
Key Detection Error/Over/run | 00h [1] | Indicates to the system that a switch closure couldn’t be |
| FFh [2] | 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 |
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| keyboard. |
Acknowledge (ACK) | FAh | Issued by the keyboard as a response to valid system |
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| 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, |
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| the keyboard issues the ACK command followed by the |
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| two IDS bytes. |
Note:
[1]Modes 2 and 3.
[2]Mode 1 only.
C.2.6 SCAN CODES
The scan codes generated by the keyboard processor are determined by the mode the keyboard is operating in.
♦Mode 1: In Mode 1 operation, the keyboard generates scan codes compatible with
♦Mode 2: Mode 2 is the default mode for keyboard operation. In this mode, the 8042 logic translates the make codes from the keyboard processor into the codes required by the BIOS. This mode was made necessary with the development of the Enhanced III keyboard, which includes additional functions over earlier standard keyboards. Applications should use BIOS function INT 16h, with AH=10h, 11h, and 12h for obtaining codes and status data. In Mode 2, the keyboard generates the Break code, a
♦Mode 3: Mode 3 generates a different scan code set from Modes 1 and 2. Code translation must be disabled since translation for this mode cannot be done.
hp/Compaq Personal Computers |
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