HT82K628 Holtek Semiconductor Inc, HT82K628 Datasheet - Page 5

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

F0H - Select alternate scan codes
This command instructs the HT82K628A to se-
lect one of the three sets of scan codes. The
HT82K628A acknowledges receipt of this com-
mand with ACK, clears both the output buffer
and the typematic key. The host then sends the
option byte and the keyboard responds with an-
other ACK. An option byte value of hex 01 se-
lects 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 before receiving the Select Alternate
Scan Codes command.
F2H - Read ID
This command requests identification informa-
tion from the HT82K628A. The HT82K628A re-
sponds 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.
F3H - Set typematic Rate/Delay
The host issues the Set Typematic Rate/Delay
command to change the typematic rate and de-
lay. The HT82K628A responds to the command
with ACK, stops scanning and waits for the sys-
tem to issue the rate/delay value byte. The
HT82K628A responds to the value byte with
another ACK, sets the rate and delay to the
value indicated, and continues scanning (if it
was previously enabled). Bit6 and 5 indicate
the delay, and bits 4, 3, 2, 1 and 0 indicate the
rate. Bit7 is always 0. The delay is equal to 1
plus the binary value bit 6 and 5, multiplied by
250ms±20%.
The period (interval from one typematic output
to the next) is determined by the following
equation:
Period = (8+A)*(2^B)*0.00417 seconds.
Preliminary
5
Where:
A = binary value of bits 2, 1, and 0.
B = binary value of bits 4, and 3.
The typematic rate is 1 for each period and are
listed as follows:
The default values for the HT82K628A are as
follows:
Typematic rate= 10.9 characters per second ±
20%
Delay = 500ms±20%
The execution of this command stops without
change to the existing rate if another command
is received instead of the rate/delay value byte.
F4H - Enable
Upon receipt of this command, the HT82K628A
will respond with ACK, clears its output buffer,
clears the last typematic key, and starts scan-
ning.
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
01111
Bit
Rate ± 20%
Typematic
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
8.0
8.0
10000
10001
10010
10011
10100
10101
10110
10111
11000
11001
11010
11011
11100
11101
11110
11111
Bit
HT82K628A
Typematic
Rate ± 20%
July 20, 2000
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