
R8C/2C Group, R8C/2D Group
15. Serial Interface
Rev.2.00
Dec 05, 2007
REJ09B0339-0200
15.2.1
Bit Rate
In UART mode, the bit rate is the frequency divided by the UiBRG (i = 0 to 2) register.
Figure 15.14
Calculation Formula of UiBRG (i = 0 to 2) Register Setting Value
i = 0 to 2
Table 15.7
Bit Rate Setting Example in UART Mode (Internal Clock Selected)
Bit Rate
(bps)
BRG
Count
Source
System Clock = 20 MHz
System Clock = 8 MHz
UiBRG
Setting Value
Actual Time
(bps)
Error (%)
UiBRG
Setting Value
Actual
Time (bps)
Error (%)
1200
f8
129 (81h)
1201.92
0.16
51 (33h)
1201.92
0.16
2400
f8
64 (40h)
2403.85
0.16
25 (19h)
2403.85
0.16
4800
f8
32 (20h)
4734.85
-1.36
12 (0Ch)
4807.69
0.16
9600
f1
129 (81h)
9615.38
0.16
51 (33h)
9615.38
0.16
14400
f1
86 (56h)
14367.82
-0.22
34 (22h)
14285.71
-0.79
19200
f1
64 (40h)
19230.77
0.16
25 (19h)
19230.77
0.16
28800
f1
42 (2Ah)
29069.77
0.94
16 (10h)
29411.76
2.12
31250
f1
39 (27h)
31250.00
0.00
15 (0Fh)
31250.00
0.00
38400
f1
32 (20h)
37878.79
-1.36
12 (0Ch)
38461.54
0.16
51200
f1
23 (17h)
52083.33
1.73
9 (09h)
50000.00
-2.34
UART mode
Internal clock selected
UiBRG register setting value =
fj
Bit Rate
× 16
- 1
Fj: Count source frequency of the UiBRG register (f1, f8, or f32)
External clock selected
fEXT
Bit Rate
× 16
- 1
fEXT: Count source frequency of the UiBRG register (external clock)
UiBRG register setting value =
i = 0 to 2