C505_9708 SIEMENS [Siemens Semiconductor Group], C505_9708 Datasheet - Page 109

• Manufacturer Part Number: C505_9708
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Figure 6-22
Baud Rate Generation for the Serial Port
Depending on the programmed operating mode different paths are selected for the baud rate clock
generation. Figure 6-22 shows the dependencies of the serial port baud rate clock generation on
the two control bits and from the mode which is selected in the special function register SCON.
6.3.3.1
The baud rate in mode 0 is fixed to :
6.3.3.2
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.
Semiconductor Group
f
Timer 1
Overflow
Note: The switch configuration shows the reset state.
OSC
Baud Rate in Mode 0
Baud Rate in Mode 2
Generator
(SRELH
SRELL)
Baud
Rate
÷
6
Mode 2 baud rate =
Mode 0 baud rate =
ADCON0.7
0
1
Mode 2
Mode 0
(BD)
Mode 1
Mode 3
2
32
SMOD
6-47
oscillator frequency
can be selected
Only one mode
SCON.7
SCON.6
(SM0/
SM1)
x
oscillator frequency
On-Chip Peripheral Components
6
÷
2
0
1
PCON.7
(SMOD)
C505 / C505C
1997-08-01
MCS02733
Baud
Rate
Clock