CHAPTER 16 ASYNCHRONOUS SERIAL INTERFACE/3-WIRE SERIAL I/O
User’s Manual U12697EJ3V0UM
274
• Baud rate capacity error range
The baud rate capacity range depends on the number of bits per frame and the counter division ratio
[1/(16 + k)].
Table 16-3 shows the relationship between the main system clock and the baud rate, Table 16-6
shows a baud rate allowable error example.
Table 16-3. Relationship Between Main System Clock and Baud Rate
Baud Rate
f
XX
= 12.5 MHz
f
XX
= 6.25 MHz
f
XX
= 3.00 MHz
(bps)
BRGC Value
Error (%)
BRGC Value
Error (%)
BRGC Value
Error (%)
2400
—
—
—
—
64H
2.34
4800
—
—
64H
1.73
54H
2.34
9600
64H
1.73
54H
1.73
44H
2.34
19200
54H
1.73
44H
1.73
34H
2.34
31250
49H
0.00
39H
0.00
28H
0.00
38400
44H
1.73
34H
1.73
24H
2.34
76800
34H
1.73
24H
1.73
14H
2.34
150K
24H
1.73
14H
1.73
—
—
300K
14H
1.73
—
—
—
—
Remark
When TM1 output is used, 150 to 38400 bps is supported (during operation at f
XX
= 12.5 MHz)
Figure 16-6. Baud Rate Allowable Error Considering Sampling Errors (When k = 0)
D0
32T
30.45T
64T
256T
288T
Ideal
sampling
point
304T
336T
D7
P
Reference timing
(Clock period T)
Stop
Stop
Stop
Start
Start
Start
352T
320T
D0
D7
P
Low-speed clock for which
normal reception is enabled
(Clock period T'')
D0
15.5T
D7
P
High-speed clock for which
normal reception is enabled
(Clock period T')
60.9T
33.55T
67.1T
301.95T
335.5T
304.5T
15.5T
Sampling error
0.5T
Remark
T: 5-bit counter source clock period
Baud rate allowable error (k = 0)
×
100 = 4.8438 (%)
±
15.5
320