C511_1 Datasheet, PDF (62/128 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

On-Chip Peripheral Units
6.3.2 Serial Port Control Register
The serial port control and status register is the special function register SCON. This register
contains not only the mode selection bits, but also the 9th data bit for transmit and receive (TB8 and
RB8) and the serial port interrupt bits (TI and RI).
Special Function Register SCON (Address 98H)
Reset Value : 00H
MSB
LSB
Bit No. 7
6
5
4
3
2
1
0
98H SM0 SM1 SM2 REN TB8 RB8 TI
RI SCON
Bit
SM0
0
0
1
1
SM2
REN
TB8
RB8
TI
RI
Function
SM1
0
1
0
1
Serial Mode Select Bits
Serial mode 0: Shift register, fixed baud rate (f_OSC/12)
Serial mode 1: 8-bit UART, variable baud rate
Serial mode 2: 9-bit UART, fixed baud rate (f_OSC/64 or f_OSC/32)
Serial mode 3: 9-bit UART, variable baud rate
Multiprocessor Communication Select
Enables the multiprocessor communication feature 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.
Receiver Enable
Enables serial reception. Set by software to enable reception. Clear by software
to disable reception.
Transmit Bit 8
Is the 9th data bit that will be transmitted in modes 2 and 3. Set or clear by
software as desired.
Receive Bit 8
In modes 2 and 3, 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.
Transmit Interrupt Flag
Is transmit interupt flag. 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.
Must be cleared by software.
Receive Interrupt Flag
Is receive interrupt flag. 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
(except see SM2). Must be cleared by software.
Semiconductor Group
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