C501 Datasheet, PDF (21/48 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

C501
Serial Interface (USART)
The serial port is full duplex and can operate in four modes (one synchronous mode, three
asynchronous modes) as illustrated in table 6. The possible baudrates can be calculated using the
formulas given in table 7.
Table 6
USART Operating Modes
Mode
0
1
2
3
SCON
SM0 SM1
0
0
0
1
1
0
1
1
Baudrate
Description
f_OSC/12
Timer 1/2 overflow rate
f_OSC/32 or f_OSC/64
Timer 1/2 overflow rate
Serial data enters and exits through R×D.
T×D outputs the shift clock. 8-bit are
transmitted/received (LSB first)
8-bit UART
10 bits are transmitted (through T×D) or
received (R×D)
9-bit UART
11 bits are transmitted (T×D) or
received (R×D)
9-bit UART
Like mode 2 except the variable baud rate
Table 7
Formulas for Calculating Baudrates
Baud Rate
derived from
Oscillator
Timer 1 (16-bit timer)
(8-bit timer with
8-bit autoreload)
Timer 2
Interface Mode
0
2
1,3
1,3
1,3
Baudrate
f_OSC/12
(2^SMOD × f_OSC) / 64
(2^SMOD × timer 1 overflow rate) /32
(2^SMOD × f_OSC) / (32 × 12 × (256-TH1))
f_OSC / (32 × (65536-(RC2H, RC2L))
Semiconductor Group
21
1997-04-01