C501_1 Datasheet, PDF (65/121 Pages) Siemens Semiconductor Group – 8-Bit Single-Chip Microcontroller

On-Chip Peripheral Components
C501
Special Function Register SCON (Address 98H)
Special Function Register SBUF (Address 99H)
Bit No.
98H
MSB
9FH
SM0
9EH
SM1
9DH
SM2
9CH
REN
9BH
TB8
9AH
RB8
Reset Value : 00H
Reset Value : XXH
LSB
99H 98H
TI
RI SCON
7
99H
6
5
4
3
2
1
Serial Interface Buffer Register
0
SBUF
Bit
SM0
SM1
SM2
REN
TB8
RB8
TI
RI
Function
Serial port 0 operating mode selection bits
SM0
0
0
1
1
SM1
0
1
0
1
Selected operating mode
Serial mode 0 : Shift register, fixed baud rate (f_OSC/6)
Serial mode 1 : 8-bit UART, variable baud rate
Serial mode 2 : 9-bit UART, fixed baud rate (f_OSC/16 or f_OSC/32)
Serial mode 3 : 9-bit UART, variable baud rate
Enable serial port multiprocessor communication in modes 2 and 3
In mode 2 or 3, if SM2 is set to 1 then RI will not be activated if the received 9th
data bit (RB8) is 0. In mode 1, if SM2 = 1 then RI will not be activated if a valid
stop bit was not received. In mode 0, SM2 should be 0.
Enable receiver of serial port
Enables serial reception. Set by software to enable serial reception. Cleared by
software to disable serial reception.
Serial port transmitter bit 9
TB8 is the 9th data bit that will be transmitted in modes 2 and 3. Set or cleared by
software as desired.
Serial port receiver bit 9
In modes 2 and 3, RB8 is the 9th data bit that was received. In mode 1, if SM2 = 0,
RB8 is the stop bit that was received. In mode 0, RB8 is not used.
Serial port transmitter interrupt flag
TI is set by hardware at the end of the 8th bit time in mode 0, or at the beginning
of the stop bit in the other modes, in any serial transmission. TI must be cleared
by software.
Serial port receiver interrupt flag
RI is set by hardware at the end of the 8th bit time in mode 0, or halfway through
the stop bit time in the other modes, in any serial reception (exception see SM2).
RI must be cleared by software.
Semiconductor Group
6-31