Enable (Hex F4); Set Typematic Rate/Delay (Hex F3) - IBM AT 5170 Technical Reference

Enable (Hex F4)
Upon receipt of this command, the keyboard responds with ACK,
clears its output buffer, and starts scanning.
Set Typematic Rate/Delay (Hex F3)
The system issues this command, followed by a parameter, to
change the typematic rate and delay. The typematic rate and
delay parameters are determined by the value of the byte
following the command. Bits 6 and 5 serve as the delay
parameter and bits 4,3,2, 1, and 0 (the least-significant bit) are
the rate parameter. Bit 7, the most-significant bit, is always O.
The delay is equal to 1 plus the binary value of bits 6 and 5
multiplied by 250 milliseconds ±200/0. The period (interval from
one typematic output to the next) is determined by the following
equation:
Period
=
(8
+
A) X (2
B )
X 0.00417 seconds, where A
=
binary
value of bits 2, 1, and 0 and B
=
binary value of bits 4 and 3.
The typematic rate (make code per second) is l/period. The
period is determined by the first equation above.
table results.
Bit 4 - 0
Typematic
Rate
±
20%
00000
30.0
00001
26.7
00010 24.0
00011 21.8
00100 20.0
00101
18.5
00110
17.1
00111
16.0
01000
15.0
01001
13.3
01010 12.0
01011
10.9
01100
10.0
01101
9.2
01110
8.0
01111
8.0
Bit 4 - 0
10000
10001
10010
10011
10100
10101
10110
10111
11000
11001
11010
11011
11100
11101
11110
11111
The following
Typematic
Rate
±
20%
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
Keyboard 4-7