Table 159. Internal Baud Rate Generator Value
FPER = 6 MHz(1)
FPER = 8 MHz(1)
FPER = 10 MHz(1)
Baud Rate
115200
57600
38400
19200
9600
SPD
SMOD1
BRL
-
Error %
-
SPD
SMOD1
BRL
-
Error %
-
SPD
SMOD1
BRL
-
Error %
-
-
-
-
-
-
-
-
-
-
-
1
1
1
1
1
1
1
1
1
1
247
243
230
204
152
3.55
0.16
0.16
0.16
0.16
1
1
1
1
1
1
1
1
1
1
245
240
223
191
126
1.36
1.73
1.36
0.16
0.16
1
1
1
1
1
1
1
1
246
236
217
178
2.34
2.34
0.16
0.16
4800
F
PER = 12 MHz(2)
FPER = 16 MHz(2)
FPER = 20 MHz(2)
Baud Rate
115200
57600
38400
19200
9600
SPD
SMOD1
BRL
-
Error %
-
SPD
SMOD1
BRL
247
239
230
204
152
48
Error %
3.55
SPD
SMOD1
BRL
245
234
223
191
126
126
Error %
1.36
-
-
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
243
236
217
178
100
0.16
2.34
0.16
0.16
0.16
2.12
1.36
0.16
1.36
0.16
0.16
0.16
0.16
4800
0.16
0.16
Notes: 1. These frequencies are achieved in X1 mode, FPER = FOSC ÷ 2.
2. These frequencies are achieved in X2 mode, FPER = FOSC
.
Baud Rate Selection (Mode 2) In mode 2, the baud rate can only be programmed to 2 fixed values: 1/16 or 1/32 of the
peripheral clock frequency.
As shown in Figure 127 the selection is done using SMOD1 bit in PCON register.
Figure 128 gives the baud rate calculation formula depending on the selection.
Figure 127. Baud Rate Generator Selection (Mode 2)
PER
CLOCK
÷ 2
0
1
÷ 16
To Serial Port
SMOD1
PCON.7
174
AT8xC51SND2C
4341D–MP3–04/05
ATMEL [ ATMEL ]
