HT82K628A

Rev. 1.60

3

April 16, 2004

Functional Description

Command from the Host

The following table shows the commands that the host

may send and their hexadecimal values.

Command

Hex Value

Set/Reset Status Indicators

ED

Echo

EE

Invalid Command

EF

Select Alternate Scan Codes

F0

Invalid Command

F1

Read ID

F2

Set Typematic Rate/Delay

F3

Enable

F4

Default Disable

F5

Set Default

F6

Set All Keys - Typematic

F7

Set All Keys - Make/Break

F8

Set All Keys - Make

F9

Set All Keys - Typematic/Make/Break

FA

Set Key Type - Typematic

FB

Set Key Type - Make/Break

FC

Set Key Type - Make

FD

Resend

FE

Reset

FF

The commands may be sent to the HT82K628A at any

time and the HT82K628A will respond within 25ms ex-

cept when performing the internal diagnostics or execut-

ing a Reset command.

EDH

- Set/Reset Status Indicators

Three status indicators on the keyboard-Num Lock,

Caps Lock, and Scroll Lock-are accessible by the host.

The HT82K628A activates or deactivates these indica-

tors when it receives a valid command-code sequence

from the system. The command sequence begins with

the command byte (hex ED). The HT82K628A responds

to the command byte with ACK, discontinues scanning,

assignments for this option byte are as follow:

Bit

Indicator

0

Scroll Lock Indicator

1

Num Lock Indicator

2

Caps Lock Indicator

3~7

Reserved (Must be 0)

If a bit for an indicator is set to 1, the indicator is turned

on. If a bit is set to 0, the indicator is turned off.

The HT82K628A responds to the option byte with ACK,

sets the indicators and if the HT82K628A was previously

enabled, continues scanning. The status of the indica-

tors will reflect the bits in the option byte and can be acti-

vated or deactivated in any combination. If another

command is received in place of the option byte, execu-

tion of the Set/Reset Mode Indicators command is

stopped, with no change to the indicator status, and the

new command is processed.

Immediately after power-on, the lights default to the off

state. If the Set Default and Default Disable commands

are received, the lamps remain in the state they were in

before the command was received.

EEH

- Echo

Echo is a diagnostic aid. When the HT82K628A re-

ceives this command, it issues a hex EE response and if

the HT82K628A was previously enabled, continues

scanning.

EFH and F1H

- Invalid Command

EFh and F1h are invalid commands and are not sup-

ported. If HT82K628A receives one of these and sends

it, the HT82K628A will not acknowledge the command,

but returns a Resend command and continues in its pre-

vious scanning state.

F0H

- Select Alternate Scan Codes

This command instructs the HT82K628A to select one of

the three sets of scan codes. The HT82K628A acknowl-

edges receipt of this command with ACK, clears both

the output buffer and the typematic key. The host then

sends the option byte and the keyboard responds with

another ACK. An option byte value of hex 01 selects

scan code set 1, hex 02 selects set 2 and hex 03 selects

code set3.

An option byte value of hex 00 causes the HT82K628A

to acknowledge with ACK and sends a byte telling the

host which scan code set is currently in use.

After establishing the new scan code set, the

HT82K628A returns to the scanning state it was in be-

fore receiving the Select Alternate Scan Codes com-

mand.

F2H

- Read ID

This command requests identification information from

the HT82K628A. The HT82K628A responds with ACK,

discontinues scanning and sends the two keyboard ID

bytes hex 83h and Abh. After the output of the second ID

byte, the HT82K628A resumes scanning.