C511 datasheet(62/128 Pages) SIEMENS

62 / 128 page

On-Chip Peripheral Units

Semiconductor Group

6-29

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

Bit

Function

SM0

SM1

Serial Mode Select Bits

Serial mode 0:

Shift register, fixed baud rate (

OSC/12)

Serial mode 1:

8-bit UART, variable baud rate

Serial mode 2:

9-bit UART, fixed baud rate (

OSC/64 or fOSC/32)

Serial mode 3:

9-bit UART, variable baud rate

SM2

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.

REN

Receiver Enable

Enables serial reception. Set by software to enable reception. Clear by software

to disable reception.

TB8

Transmit Bit 8

Is the 9th data bit that will be transmitted in modes 2 and 3. Set or clear by

software as desired.

RB8

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.

SM0

SM1

SM2

REN

98H

SCON

Bit No.

MSB

LSB

TB8

RB8

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