Z8
®
CPU
User Manual
UM001604-0108
Serial Input/Output
117
To configure Z8
®
CPU for a specific bit rate, appropriate values as determined by the
above equation must be loaded into registers PRE0
(
F5h
) and T0 (
F4h
). PRE0 also controls the counting mode for T0 and should therefore be
set to CONTINUOUS mode (D0 = 1).
For example, given an input clock frequency (XTAL) of 11.9808 MHz and a selected bit
rate of 1200 bits per second, the equation is satisfied by p = 39 and t = 2. Counter/Timer
T0 should be set to
02h
. With T0 in Continuous Mode, the value of PRE0 becomes
9Dh
).
lists several commonly used bit rates and the values of XTAL, p, and t required to
derive them. This list is presented for convenience and is not intended to be exhaustive.
Table 24. Bit Rates
Bit Rate
7,3728
7,9872
9,8304
11,0592
11,6736
11,9808
12,2880
p
t
p
t
p
t
p
t
p
t
p
t
p
t
19200
3
1
–
–
4
1
–
–
–
–
–
–
5
1
9600
3
2
–
–
4
2
9
1
–
–
–
–
5
2
4800
3
4
13
1
4
4
9
2
19
1
–
–
5
4
2400
3
8
13
2
4
8
9
4
19
2
39
1
5
8
1200
3
16
13
4
4
16
9
8
19
4
39
2
5
16
600
3
32
13
8
4
32
9
16
19
8
39
4
5
32
300
3
64
13
16
4
64
9
32
19
16
39
8
5
64
150
3
128 13
32
4
128
9
64
19
32
39
16
5
128
110
3
175
3
189
4
175
5
157
4
207 17
50
8
109
Figure 108. Prescaler 0 Register Bit-Rate Generation
D7 D6 D5 D4 D3 D2 D1 D0
(Write-Only)
Prescalar 0 Register (PRE0)
Register F5h
Count Mode
0 = T
0
Single Pass
(Range: 1-64 decimal, 01h–00h)
(Range: 1-64)
1 = T
0
Modulo-n