C515 Datasheet, PDF (31/55 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

C515
Timer 1
Overflow
ADCON.7
SCON.7
(BD)
SCON.6
(SM0/
0
f _OSC/2
÷ 39
1
Mode 1
SM1)
Mode 3
÷2
Mode 2
÷6
Mode 0
Only one mode
can be selected
Note: The switch configuration shows the reset state.
PCON.7
(SMOD)
0
Baud
1
Rate
Clock
MCB03206
Figure 13
Block Diagram of Baud Rate Generation for the Serial Interface
Table 6 below lists the values/formulas for the baud rate calculation of the serial interface with its
dependencies of the control bits BD and SMOD.
Table 6
Serial Interface - 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 Baud Rate Calculation
BD
SMOD
–
–
f_OSC / 12
0
X
Controlled by timer 1 overflow :
(2^SMOD × timer 1 overflow rate) / 32
1
X
Controlled by system clock divider circuits :
(2^SMOD × f_OSC) / 2496
–
0
1
f_OSC / 64
f_OSC / 32
Semiconductor Group
31
1997-08-01