Keyboard

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

8088-/8086-based systems. To enter Mode 1, the scan code translation function of the keyboard controller must be disabled. Since translation is not performed, the scan codes generated in Mode 1 are identical to the codes required by BIOS. Mode 1 is initiated by sending command F0h with the 01h option byte. Applications can obtain system codes and status information by using BIOS function INT 16h with AH=00h, 01h, and 02h.

■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 two-byte sequence that consists of a Make code immediately preceded by F0h (i.e., Break code for 0Eh is “F0h 0Eh”).

■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.

NOTES:

Table C-2.Keyboard Scan Codes

Key

 

 

 

Make/Break Codes (Hex)

 

 

 

 

 

 

 

 

 

 

 

Pos.

Legend

Mode 1

Mode 2

Mode 3

 

 

 

 

 

1

Esc

01/81

76/F0 76

08/na

 

 

 

 

 

 

2

F1

 

3B/BB

05/F0 05

07/na

 

 

 

 

 

 

3

F2

 

3C/BC

06/F0 06

0F/na

 

 

 

 

 

 

4

F3

 

3D/BD

04/F0 04

17/na

 

 

 

 

 

 

5

F4

 

3E/BE

0C/F0 0C

1F/na

 

 

 

 

 

 

6

F5

 

3F/BF

03/F0 03

27/na

 

 

 

 

 

 

7

F6

 

40/C0

0B/F0 0B

2F/na

 

 

 

 

 

 

8

F7

 

41/C1

83/F0 83

37/na

 

 

 

 

 

 

9

F8

 

42/C2

0A/F0 0A

3F/na

 

 

 

 

 

10

F9

43/C3

01/FO 01

47/na

 

 

 

 

 

 

11

F10

 

44/C4

09/F0 09

4F/na

 

 

 

 

 

12

F11

57/D7

78/F0 78

56/na

 

 

 

 

 

 

13

F12

 

58/D8

07/F0 07

5E/na

 

 

 

 

 

 

 

Technical Reference Guide

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C-11