HT82K629A
Rev. 1.60 6 June 11, 2008
F5H - Default Disable
The Default Disable command resets all conditions to
the power on default states. The HT82K629A will
respond with
ACK
, clears its output buffer, sets the de
-
fault typematic rate/delay, and clears the last typematic
key. The HT82K629A then stops scanning and awaits
further command.
F6H - Set Default
The Set Default command resets all conditions to the
power on default states. The HT82K629A will respond
with ACK, clears its output buffer, sets the default key
typematic rate/delay, and clears the last typematic key
then continues scanning.
F7H, F8H, F9H, FAH - Set All Keys
Since HT82K629A do not support keyboard code set 3
format, so it will not acknowledge the command but re
-
turns a Resend command and continues in its previous
scanning state.
FBH, FCH, FDH - Set Key Type
Since HT82K629A do not support keyboard code set 3
format, so it will not acknowledge the command but re
-
turns a Resend command and continues in its previous
scanning state.
FEH - Resend
The host sends this command when it detects an error in
any transmission from the HT82K629A. It is sent only af-
ter a data transmission and before the host allows the
next data output. When a Resend is received, the
HT82K629A sends the previous output again (unless
the previous output was Resent, in which case the
HT82K629A sends the last byte before the Resend
command).
Commands to the Host
The following table shows the commands that the
HT82K629A may send to the host and their hexadeci
-
mal values.
Command Hex Value
Key Detection Error/Overrun 00 (Code Set 2)
Keyboard ID 83AB
Bat Completion Code AA
Bat Failure Core FC
Echo EE
Acknowledge FA
Resend FE
Key Detection Error/Overrun FF (Code Set 1)
00H or FFH - Key Detection Error
The HT82K629A sends a key detection error character if
conditions in the keyboard make it impossible to identify
a switch closure. If the HT82K629A is using scan code
set 1, the code is FFH. For sets 2, the code is 00H.
00H or FFH - Overrun
An overrun character is placed in the HT82K629A buffer
and replaces the last code when the buffer capacity has
been exceeded. The code is sent to the host when it
reaches the top of the buffer queue. If the HT82K629A is
using scan code set 1, the code is
FFH
. For sets 2, the
code is 00H.
83AbH - Keyboard ID
The keyboard ID consists of 2 bytes, Hex 83AbH. The
HT82K629A responds to the Read ID with ACK, discon
-
tinues scanning and sends 2 ID bytes. The low byte is
sent first followed by the high byte. Following the output
of Keyboard ID, the HT82K629A begins scanning.
EEH - Echo
The HT82K629A sends this code in response to an
Echo command.
AAH - BAT Completion Code
Following a satisfactory completion of the BAT, the
HT82K629A sends AAH. Any other code indicates key
-
board failure.
FCH - BAT Failure Code
If a BAT failure occurs, the HT82K629A sends this code,
discontinues scanning and waits for a host response or
reset.
FEH - Resend
The HT82K629A issues a Resend command following
receipt of an invalid input or any input with incorrect par
-
ity. If the host sends nothing to the HT82K629A, no re
-
sponse is required.
Data Communications
·
Data output
¨
If CLK=0, no transmission (keyboard is inhibited).
¨
If CLK=1, DATA=0, no transmission (system re
-
quest to send).
¨
If CLK=1, DATA=1, transmission permitted.
¨
Data will be valid before the trailing edge and be
-
yond the leading edge of the clock.
¨
The KB checks the clock line for an active level ev
-
ery 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 clock line state at inter
-
vals of 10ms.