HT82K28 データシートの表示（PDF） - Holtek Semiconductor

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HT82K28

Win98 Keyboard Encoder

Holtek Semiconductor 

b4~b0

00000

00001

00010

00011

00100

00101

00110

00111

01000

01001

01010

01011

01100

01101

01110

01111

Typematic

rate

30.0

26.7

24.0

21.8

20.0

18.5

17.1

16.0

15.0

13.3

12.0

10.9

10.0

9.2

8.6

8.0

b4~b0

10000

10001

10010

10011

10100

10101

10110

10111

11000

11001

11010

11011

11100

11101

11110

11111

Typematic

rate

7.5

6.7

6.0

5.5

5.0

4.6

4.3

4.0

3.7

3.3

3.0

2.7

2.5

2.3

2.1

2.0

· Default

¨ delay: 500ms± 20%

¨ typematic rate=10.9 characters/sec± 20%

Commands to the system

00: keyboard detect a error/overrun (set 2, set 3)

AB,83: keyboard ID

AA: BAT completion

FC: BAT failure

EE: Echo

FA: Acknowledge

FE: Resend

FF: Keyboard detects a overrun (set 1)

· FA: Acknowledge

If the KB (Keyboard) receives any valid input

except EE (echo) and resend (FE) then send

an FA to the system first.

If the command is EE, then send an EE back

to the system.

If the command is FE, then send the last key

code to system.

If there is an interrupt while sending FA, the

KB discards the FA and accepts the command

from the system and processes it.

· 00/FF: Key overrun

If the keyboard detects an overrun error, the

KB sends an overrun error code to the system.

mode 1: FF

mode 2,3: 00

HT82K28A

· FE: Resend

The KB issues an FE when there is a parity

error in transmission.

Data communications

· Data output

¨ If CLK=0, no transmission (keyboard inhib-

ited).

¨ If CLK=1, DATA=0, no transmission (sys-

tem request to send).

¨ If CLK=1, DATA=1, transmission permit-

ted.

¨ Data will be valid before the trailing edge

and beyond the leading edge of the clock.

¨ The KB checks the clock line for an active

level at least every 60ms.

¨ If line contention occurs (system brings the

clock low before the tenth clock), set

clock=data=high.

· Data input

¨ The system overrides the clock line for at

least 60ms

¨ The keyboard checks the state of the clock

line at intervals of no more than 10ms

¨ If a system request-to-send is detected, the

keyboard counts 11 data bits.

¨ Data will be valid before the rising edge and

beyond the falling edge

¨ After the 10th bit, the keyboard checks for

an active level on the "data" line. If the line

is active it is forced to be inactive, and

counts one more bit.

Note: This action signals the system that

the keyboard has received its data.

Upon reception of this signal, the

system returns to the ready state, in

which it can accept keyboard outputs

or goes to the inhibit state until it is

ready.

If the keyboard "data" line is found to be at an

inactive level following the 10th bit, a frame

error has occurred, and the keyboard contin-

ues to count until the "data" line becomes ac-

tive. The keyboard then makes the "data" line

inactive and sends a Resend.

8

February 16, 2000

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