CHAPTER 11 SERIAL INTERFACE FUNCTION
User’s Manual U15109EJ3V0UD
446
(b) Baud rate
The baud rate transmit/receive clock that is generated is obtained by dividing the main clock.
•
Generation of baud rate transmit/receive clock using main clock
The transmit/receive clock is obtained by dividing the main clock. The following equation is used to
obtain the baud rate from the main clock.
<When 8
≤≤≤≤
k
≤≤≤≤
255>
[Baud rate] =
[Hz]
f
XX
: Main clock oscillation frequency
m:
Value set by TPSn3 to TPSn0 (0
≤
m
≤
9)
k:
Value set by MDLn7 to MDLn0 (8
≤
k
≤
255)
•
Baud rate tolerance
The baud rate tolerance depends on the number of bits in a frame and the counter division ratio
[1/(16 + k)].
Table 11-13 shows the relationship between the main clock and the baud rate, and Figure 11-48 shows
an example of the allowable baud rate error range.
Table 11-13. Relationship Between Main Clock and Baud Rate
f
XX
= 20 MHz
f
XX
= 18.87 MHz
f
XX
= 16 MHz
Baud Rate
(bps)
k
m
Error (%)
k
m
Error (%)
k
m
Error (%)
32
–
–
–
–
–
–
–
–
–
64
–
–
–
–
–
–
244
9
0.06
128
152
9
–0.39
144
9
–0.02
244
8
0.06
300
130
8
0.16
123
8
–0.12
208
7
0.16
600
130
7
0.16
123
7
–0.12
208
6
0.16
1200
130
6
0.16
123
6
–0.12
208
5
0.16
2400
130
5
0.16
123
5
–0.12
208
4
0.16
4800
130
4
0.16
123
4
–0.12
208
3
0.16
9600
130
3
0.16
123
3
–0.12
208
2
0.16
19200
130
2
0.16
123
2
–0.12
208
1
0.16
38400
130
1
0.16
123
1
–0.12
208
0
0.16
76800
130
0
0.16
123
0
–0.12
104
0
0.16
150000
67
0
–0.50
63
0
–0.16
53
0
0.63
300000
33
0
1.01
31
0
1.45
27
0
–1.24
524000
19
0
0.44
18
0
0.03
15
0
1.78
1250000
8
0
0.00
–
–
–
–
–
–
Remark
f
XX
: Main clock oscillation frequency
f
XX
2
m+1
×
k