HT82K28A datasheet(5/20 Pages) HOLTEK

5 / 20 page

HT82K28A

February 16, 2000

Power-on

Two important activities take place when power

is first applied to the keyboard. The first is the

presence of an H/W signal POR (Power-On-Re-

set) that resets the keyboard processor. The sec-

ond activity is the running of the self test BAT

(Basic Assurance Test) routine.

PC-type/mode/code set

The following table describes the relationship

between different computer types, the working

mode and the code sets.

PS/2 30

mode 1

code set 1

PC-AT

mode 2

code set 2

PS/2 50

mode 2

code set 2

PS/2 60

mode 2

code set 2

PS/2 80

mode 3

code set 3

The mode can be changed between mode 2 & 3.

Keys

· For code set 1, 2

All keys except the PAUSE key have a make

and break code. The PAUSE key has a make

code only.

The defaults except for PAUSE are make/

break/typematic. In mode 1, 2 and 3 the key

type may be changed to be one of the follow-

ing:

Typematic

Make/break

Make

Typematic/make/break

All keys except PAUSE are typematic.

Typematic means that the KB keeps send-

ing make codes if the key is held down.

The data report is according to the

typematic rate/delay:

Default values are: delay 500ms ± 20%

10.9 char/sec ± 20%

The typematic rate and delay can be modi-

fied with the F3 command.

If two or more keys are held down, only the

last key pressed repeats at the typematic

rate.

Typematic operation stops when the last

key pressed is released even if other keys

are still held down.

If a key is pressed and held down while key-

board transmission is inhibited, only the

first make code is stored in the buffer over-

flow as a result of typematic action.

Four key types are supported as shown:

Key type

press

hold

release

Typematic

Make/break

Make

Typematic/

make/break

make1

make2

break

Note: "make1" send out only one make

code.

"Make2" continue sending out make

codes until key is released.

"X" nothing sent out.

· For code set 3

Typematic

Make/break

Make

Typematic/make/break

Can be configured by command

Time interval between phantoms

The time interval between two continuous error

codes 00/FF sent while phantom detected=

1000ms ± 20%

P O R

R es et

150 m s ~ 2 s

300 m s ~ 500 m s

450 m s ~ 2 . 5 s e c

P o w e r on s t ar t

B A T s t a r t ed

B A T com pl et e

m ode1

m ode2

m ode3

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