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CHAPTER 13 SERIAL INTERFACE UART
Preliminary User’s Manual U14581EJ3V0UM00
• Error tolerance range for baud rates
The tolerance range for baud rates depends on the number of bits per frame and the counter’s division
rate [1/(16 + k)].
Table 13-3 describes the relation between the main system clock and the baud rate and Figure 13-5 shows
an example of a baud rate error tolerance range.
Table 13-3. Relation between Main System Clock and Baud Rate
Baud Rate
f
X
= 8.386 MHz
(bps)
BRGC Set Value
Error (%)
600
7BH
1.10
1,200
6BH
1.10
2,400
5BH
1.10
4,800
4BH
1.10
9,600
3BH
1.10
19,200
2BH
–1.3
31,250
21H
1.10
38,400
1BH
1.10
76,800
0BH
1.10
115,200
01H
1.03
Remark
f
X
: Main system clock oscillation frequency
Figure 13-5. Error Tolerance (When k = 0) Including Sampling Errors
Basic timing
(clock cycle T)
START
D0
D7
P
STOP
High-speed clock
(clock cycle T’)
enabling normal
reception
START
D0
D7
P
STOP
Low-speed clock
(clock cycle T”)
enabling normal
reception
START
D0
D7
P
STOP
32T
64T
256T
288T
320T
352T
Ideal
sampling
point
304T
336T
30.45T
60.9T
304.5T
15.5T
15.5T
0.5T
Sampling error
33.55T
67.1T
301.95T
335.5T
Remark
T: 5-bit counter’s source clock cycle
Baud rate error tolerance (when k = 0) =
±
15.5
×
100 = 4.8438 (%)
320
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