7

* This specification are subject to be changed without notice.

EM83049

KEYBOARD ENCODER

5.2.1997

Keyboards ID ( Hex 83AB )

The 2 byte ID is issued to respond to READ ID command. The low byte is sent first, followed by the high byte.

Keyboard buffer Overrun ( Hex 00 or FF )

If keyboard buffer overflows, the overrun code will replace the last byte in the buffer. If the keyboard is using

scan code set 1 , the code is hex FF. For sets 2 and 3, the code is hex 00.

Resend ( Hex FE )

When the keyboard receives an invalid input or any input with incorrect parity, the RESEND command is sent.

Keyboard Scan Code Table

The keyboard contains 3 scan code sets. The system defaults to scan code set 2, but can be switched to set 1 or

set 3 . The following tables show the key numbers and three scan code sets in hexadecimal values. All the keys

are typematics except for the pause key. When a key is pressed down, the make scan code is sent to the

system. When the key is released, its break code is sent. If two or more keys are held down, only the last key

pressed repeats at the typematic rate. Typematic operation stops when the last pressed key is released, even if

other keys are being released or some other keys are still held down.

The following table shows three scan code sets used in the keyboard.

scan code set 1

Key Number

Make code

Break code

Key Number

Make code

Break code

1

29

A9

47

2D

AD

202

82

48

2E

AE

303

83

49

2F

AF

4

04

84

50

30

B0

5

05

85

51

31

B1

6

06

86

52

32

B2

7

07

87

53

33

B3

8

08

88

54

34

B4

9

09

89

55

35

B5

10

0A

8A

57

36

B6

11

0B

8B

58

1D

9D

12

0C

8C

60

38

B8

13

0D

8D

61

39

B9

15

0E

8E

62

E0 38

E0 B8

16

0F

8F

64

E0 1D

E0 9D

17

10

90

90

45

C5

18

11

91

91

47

C7

19

12

92

92

4B

CB

20

13

93

93

4F

CF

21

14

94

96

48

C8

22

15

95

97

4C

CC