Example Of Relationship Between System Clock And Baud Rate - NEC PD789488 User Manual

The baud rate transmit/receive clock to be generated is either a divided system clock signal, or a signal
obtained by dividing the clock input to the ASCK20 pin.
(a) Generation of UART baud rate transmit/receive clock form system clock
The transmit/receive clock is generated by dividing the system clock. The baud rate of a clock generated
from the system clock is estimated by using the following expression.
[Baud rate] =
n + 1
2
f : Main system clock oscillation frequency
X
n: Values in Figure 11-6, determined by the values of TPS200 to TPS203 (2 ≤ n ≤ 8)
Table 11-3. Example of Relationship Between System Clock and Baud Rate
Baud Rate (bps)
1,200
2,400
4,800
9,600
19,200
38,400
76,800
Caution Do not select n = 1 during operation at f
rated range.
CHAPTER 11 SERIAL INTERFACE 20
f
X
[bps]
× 8
n BRGC20 Set Value
8 70H
7 60H
6 50H
5 40H
4 30H
3 20H
2 10H
X
User's Manual U15331EJ4V1UD
f = 5.0 MHz
X
1.73
> 2.5 MHz because the resulting baud rate exceeds the
Error (%)
f = 4.9152 MHz
X
0
195