C517A_99 Datasheet, PDF (141/218 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

On-Chip Peripheral Components
C517A
6.5.1.4.1 Baud Rate in Mode 0
The baud rate in mode 0 is fixed to :
Mode 0 baud rate = ^{oscillator frequency}
12
6.5.1.4.2 Baud Rate in Mode 2
The baud rate in mode 2 depends on the value of bit SMOD in special function register PCON. If
SMOD = 0 (which is the value after reset), the baud rate is 1/64 of the oscillator frequency. If SMOD
= 1, the baud rate is 1/32 of the oscillator frequency.
2 ^SMOD
Mode 2 baud rate =
x oscillator frequency
64
6.5.1.4.3 Baud Rate in Mode 1 and 3
In these modes the baud rate is variable and can be generated alternatively by the programmable
baud rate generator or by timer 1.
Using the Programmable Baud Rate Generator:
In modes 1 and 3, the C517A can use an internal baud rate generator for serial interface 0. To
enable this feature, bit BD (bit 7 of special function register ADCON0) must be set. Bit SMOD
(PCON.7) controls a divide-by-2 circuit which affects the input and output clock signal of the baud
rate generator. After reset the divide-by-2 circuit is active and the resulting overflow output clock will
be divided by 2. The input clock of the baud rate generator is f_OSC/2.
Baud Rate Generator
S0RELH .1 .0
S0RELL
f_OSC /2 _{Input Clock}
10-Bit Timer
Owerflow
PCON.7
(SMOD)
÷2
0
Baud
1
Rate
Clock
MCS03330
Figure 6-34
Serial Interface 0 Input Clock using the Baud Rate Generator
Semiconductor Group
6-75