User`s manual

Semiconductor Group 6-31
On-Chip Peripheral Components
C501
Special Function Register SCON (Address 98
H
) Reset Value : 00
H
Special Function Register SBUF (Address 99
H
) Reset Value : XX
H
Bit Function
SM0
SM1
Serial port 0 operating mode selection bits
SM2 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.
REN Enable receiver of serial port
Enables serial reception. Set by software to enable serial reception. Cleared by
software to disable serial reception.
TB8 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.
RB8 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.
TI 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.
RI 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.
9F
H
9E
H
9D
H
9C
H
9B
H
9A
H
99
H
98
H
SM0 SM1 SM2 REN98
H
SCON
Bit No. MSB LSB
TB8 RB8 TI RI
99
H
SBUF
76543210
Serial Interface Buffer Register
SM0 SM1 Selected operating mode
0 0 Serial mode 0 : Shift register, fixed baud rate (
f
OSC
/6)
0 1 Serial mode 1 : 8-bit UART, variable baud rate
1 0 Serial mode 2 : 9-bit UART, fixed baud rate (
f
OSC
/16 or f
OSC
/32)
1 1 Serial mode 3 : 9-bit UART, variable baud rate