CHAPTER 12 SERIAL INTERFACE 20
User’s Manual U15075EJ1V0UM00
220
The baud rate transmit/receive clock to be generated is either a signal scaled from the system clock, or a
signal scaled from the clock input to the ASCK20 pin.
(a) Generation of baud rate transmit/receive clock form system clock
The transmit/receive clock is generated by scaling the system clock. The baud rate of a clock
generated from the system clock is estimated by using the following expression.
[Baud rate] = [Hz]
f
X
: Main system clock oscillation frequency
n: Values in Figure 12-6, determined by the values of TPS200 to TPS203 (2
≤
n
≤
8)
Table 12-3. Example of Relationships Between System Clock and Baud Rate
Error (%)
Baud Rate (bps)
n
BRGC20 Set Value
f
X
= 5.0 MHz
f
X
= 4.9152 MHz
1,200
8
70H
2,400
7
60H
4,800
6
50H
9,600
5
40H
19,200
4
30H
38,400
3
20H
76,800
2
10H
1.73
0
Caution
Do not select n = 1 during operation at f
X
= 5.0 MHz because the resulting baud rate exceeds
the rated range.
f
X
2
n + 1
×
8
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