C509-L_97 Datasheet, PDF (164/290 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

On-Chip Peripheral Components
C509-L
Figure 6-38 shows the configuration for the baud rate generation of serial channel 0.
Figure 6-38
Baud Rate Generation for Serial Channel 0
Depending on the programmed operating mode different paths are selected for the baud rate clock
generation. Table 6-12 shows the dependencies of the serial port 0 baud rate clock generation from
the 3 control bits and from the mode which is selected in the special function register S0CON.
Table 6-12
Serial Interface 0 - Baud Rate Dependencies
Serial Interface 0
Operating Modes
Mode 0 (Shift Register)
Mode 1 (8-bit UART)
Mode 3 (9-bit UART)
Mode 2 (9-bit UART)
Active Control Bits
BD
S0P SMOD
–
–
–
X
X
X
–
–
X
Baud Rate Clock Generation
Fixed baud rate clock fosc/6
BD=0: Timer 1 overflow is used for
baud rate generation; SMOD
controls a divide-by-2 option.
BD=1: Baud rate generator is used for
rate generation; S0P and
SMOD control two divide-by-2
options.
Fixed baud rate clock fosc/16
(SMOD=1) or fosc/32 (SMOD=0)
Note: If the internal baud generator is selected in mode 1,3, S0P has no effect on the prescaler function if the
reload value in S0RELL/S0RELH is 3FF_H (S0P divider ratio of ÷1 implicitly selected).
Semiconductor Group
6-86
1997-10-01