Datasheet

174
4341H–MP3–10/07
AT8xC51SND2C/MP3B
Notes: 1. These frequencies are achieved in X1 mode, F
PER
= F
OSC
÷ 2.
2. These frequencies are achieved in X2 mode, F
PER
= F
OSC
.
20.4.5 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 periph-
eral clock frequency.
As shown in Figure 20-14 the selection is done using SMOD1 bit in PCON register.
Figure 20-15 gives the baud rate calculation formula depending on the selection.
Figure 20-14. Baud Rate Generator Selection (Mode 2)
Table 20-2. Internal Baud Rate Generator Value
Baud
Rate
F
PER
= 6 MHz
(1)
F
PER
= 8 MHz
(1)
F
PER
= 10 MHz
(1)
SPD
SMOD
1 BRL
Error
% SPD
SMOD
1 BRL
Error
% SPD
SMOD
1 BRL
Error
%
115200 - - - - - - - - - - - -
57600 - - - - 1 1 247 3.55 1 1 245 1.36
38400 1 1 246 2.34 1 1 243 0.16 1 1 240 1.73
19200 1 1 236 2.34 1 1 230 0.16 1 1 223 1.36
9600 1 1 217 0.16 1 1 204 0.16 1 1 191 0.16
4800 1 1 178 0.16 1 1 152 0.16 1 1 126 0.16
Baud
Rate
F
PER
= 12 MHz
(2)
F
PER
= 16 MHz
(2)
F
PER
= 20 MHz
(2)
SPD
SMOD
1 BRL
Error
% SPD
SMOD
1 BRL
Error
% SPD
SMOD
1 BRL
Error
%
115200 - - - - 1 1 247 3.55 1 1 245 1.36
57600 1 1 243 0.16 1 1 239 2.12 1 1 234 1.36
38400 1 1 236 2.34 1 1 230 0.16 1 1 223 1.36
19200 1 1 217 0.16 1 1 204 0.16 1 1 191 0.16
9600 1 1 178 0.16 1 1 152 0.16 1 1 126 0.16
4800 1 1 100 0.16 1 1 48 0.16 1 0 126 0.16
0
1
SMOD1
PCON.7
PER
CLOCK
÷ 2
÷ 16
To Serial Port