C515A_9708 Datasheet, PDF (97/182 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

On-Chip Peripheral Components
C515A
6.3.3.1 Baud Rate in Mode 0
The baud rate in mode 0 is fixed to :
Mode 0 baud rate = ^{oscillator frequency}
12
6.3.3.2 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
6.3.3.3 Baud Rate in Mode 1 and 3
In these modes the baud rate is variable and can be generated alternatively by a programmable
baud rate generator or by timer 1.
6.3.3.3.1 Using the Programmable Baud Rate Generator
In modes 1 and 3, the C515A can use an internal baud rate generator for the serial port. 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.
Figure 6-24
Serial Port Input Clock when using the Programmable Baud Rate Generator
Semiconductor Group
6-46
1997-08-01