AT89C5132
Figure 18-13. Baud Rate Formulas (Modes 1 and 3)
2SMOD1 ⋅ FPER
6(1-SPD) ⋅ 32 ⋅ (256 -BRL)
2SMOD1 ⋅ FPER
Baud_Rate=
Baud_Rate=
TH1= 256 -
6 ⋅ 32 ⋅ (256 -TH1)
2SMOD1 ⋅ FPER
6(1-SPD) ⋅ 32 ⋅ Baud_Rate
2SMOD1 ⋅ FPER
BRL= 256 -
192 ⋅ Baud_Rate
a. IBRG Formula
b. T1 Formula
Table 90. Baud Rate Generator Configuration
FPER = 6 MHz(1)
FPER = 8 MHz(1)
FPER = 10 MHz(1)
SMOD
Baud
Rate
SMOD
Error
%
SMOD
1
Error
%
Error
%
SPD
1
-
BRL
-
SPD
BRL
-
SPD
1
BRL
115200
57600
38400
19200
9600
-
-
-
-
-
-
-
-
-
-
-
-
-
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
FPER = 12 MHz(2)
SMOD
FPER = 16 MHz(2)
SMOD
FPER = 20 MHz(2)
SMOD
Baud
Rate
Error
%
Error
%
Error
%
SPD
1
BRL
SPD
1
1
1
1
1
1
1
BRL
247
239
230
204
152
48
SPD
1
1
1
1
1
1
0
BRL
245
234
223
191
126
126
115200
57600
38400
19200
9600
-
-
-
-
1
1
1
1
1
1
3.55
2.12
0.16
0.16
0.16
0.16
1
1
1
1
1
1
1.36
1.36
1.36
0.16
0.16
0.16
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
4800
Notes: 1. These frequencies are achieved in X1 mode, FPER = FOSC ÷ 2.
.
2. These frequencies are achieved in X2 mode, FPER = FOSC
18.4.5
Baud Rate Selection
(Mode 2)
In mode 2, the baud rate can only be programmed to two fixed values: 1/16 or 1/32 of the periph-
eral clock frequency.
As shown in Figure 18-14 the selection is done using SMOD1 bit in PCON register.
Figure 18-15 gives the baud rate calculation formula depending on the selection.
113
4173E–USB–09/07
ATMEL [ ATMEL ]
