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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>
f
xx
[Baud rate] =
× k
m+1
2
f
: Main clock oscillation frequency
xx
m : Value set by TPSn2 to TPSn0 (0 ≤ m ≤ 5)
: Value set by MDLn7 to MDLn0 (8 ≤ k ≤ 255)
k
•
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 10-8 shows the relation between the main clock and the baud rate and Figure 10-33 shows an example
of the baud rate tolerance.
Table 10-8. Relation between Main Clock and Baud Rate
Baud Rate
fxx = 17 MHz
(bps)
k
1200
221
5
2400
221
4
4800
221
3
9600
221
2
19200
221
1
31250
136
1
38400
221
0
76800
111
0
150 K
55
0
300 K
28
0
Remark
fxx: Main clock oscillation frequency
CHAPTER 10
SERIAL INTERFACE FUNCTION
[Hz]
m
Error (%)
k
0.16
130
0.16
130
0.16
130
0.16
130
0.16
130
0.00
160
0.16
130
−0.29
65
0.62
33
−1.18
16
fxx = 10 MHz
m
Error (%)
5
0.16
130
4
0.16
130
3
0.16
130
2
0.16
130
1
0.16
130
0
0.00
80
0
0.16
65
0
0.16
33
−1.36
0
16
0
1.73
8
fxx = 5 MHz
k
m
Error (%)
4
0.16
3
0.16
2
0.16
1
0.16
0
0.16
0
0.00
0
0.16
−1.36
0
0
1.73
0
1.73
293
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