C509-L_97 Datasheet, PDF (165/290 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

On-Chip Peripheral Components
C509-L
Baud Rate in Mode 0
The baud rate in mode 0 is fixed to:
Mode 0 baud rate = ^{oscillator frequency}
6
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 1/32 of the oscillator frequency.
If SMOD = 1, the baud rate is 1/16 of the oscillator frequency.
2 ^SMOD
Mode 2 baud rate =
x oscillator frequency
32
Baud Rate in Mode 1 and 3
In these modes the baud rate is variable and can be generated alternatively by a baud rate
generator or by timer 1.
Using the baud rate generator:
In modes 1 and 3, the C509-L 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 S0P
(PRSC.6) and SMOD (PCON.7) control divide-by-2 circuits which affect the input and output clock
signal of the baud rate generator. After reset both divide-by-2 circuits are active. So, the input clock
of the baud rate generator is f_OSC/2 and the resulting overflow output clock will be divided by 2.
Figure 6-39
Serial Interface 0 Input Clock using the Baud Rate Generator
Semiconductor Group
6-87
1997-10-01