HT82K628 Holtek Semiconductor Inc, HT82K628 Datasheet - Page 4

• Manufacturer Part Number: HT82K628
• Description: Windows 2000 Keyboard Encoder
• Manufacturer: Holtek Semiconductor Inc

Functional Description
Command from the host
The following table shows the commands that
the host may send and their hexadecimal val-
ues.
The commands may be sent to the HT82K628A
at any time and the HT82K628A will respond
within 25ms except when performing the inter-
nal diagnostics or executing 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 deac-
tivates these indicators when it receives a valid
command-code sequence from the system. The
command sequence begins with the command
Set/Reset Status Indicators
Echo
Invalid Command
Select Alternate Scan Codes
Invalid Command
Read ID
Set Typematic Rate/Delay
Enable
Default Disable
Set Default
Set All Keys - Typematic
Set All Keys - Make/Break
Set All Keys - Make
Set All Keys - Typematic/
Make/Break
Set Key Type - Typematic
Set Key Type - Make/Break
Set Key Type - Make
Resend
Reset
Command
Hex Value
ED
EE
FD
EF
FA
FB
FC
FE
FF
F0
F1
F2
F3
F4
F5
F6
F7
F8
F9
Preliminary
4
byte (hex ED). The HT82K628A responds to the
command byte with ACK, discontinues scan-
ning, assignments for this option byte are as
follow:
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 indicators will re-
flect 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 op-
tion byte, execution of the Set/Reset Mode Indi-
cators 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 re-
main in the state they were in before the com-
mand was received.
EEH - Echo
Echo is a diagnostic aid. When the HT82K628A
receives this command, it issues a hex EE re-
sponse and if the HT82K628A was previously
enabled, continues scanning.
EFH and F1H - Invalid command
EFh and F1h are invalid commands and are not
supported. If HT82K628A receives one of these
and sends it, the HT82K628A will not acknowl-
edge the command, but returns a Resend com-
mand and continues in its previous scanning
state.
0
1
2
3~7
Bit
Scroll Lock Indicator
Num Lock Indicator
Caps Lock Indicator
Reserved (Must be 0)
Indicator
HT82K628A
July 20, 2000