9202 datasheet(62/175 Pages) STMICROELECTRONICS

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UPSD3254A, UPSD3254BV, UPSD3253B, UPSD3253BV

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Table 44. Description of the SCON Bits

Bit

Symbol

Function

SM0

(SM1,SM0)=(0,0): Shift Register. Baud rate = fOSC/12

(SM1,SM0)=(1,0): 8-bit UART. Baud rate = variable

(SM1,SM0)=(0,1): 8-bit UART. Baud rate = fOSC/64 or fOSC/32

(SM1,SM0)=(1,1): 8-bit UART. Baud rate = variable

6SM1

5SM2

Enables the multiprocessor communication features in Mode 2 and 3. In Mode 2 or 3, if

SM2 is set to '1,' RI will not be activated if its received 8th data bit (RB8) is '0.' In Mode

1, if SM2=1, RI will not be activated if a valid Stop Bit was not received. In Mode 0, SM2

should be '0'

4REN

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

disable reception

3TB8

The 8th data bit that will be transmitted in Modes 2 and 3. Set or clear by software as

desired

2RB8

In Modes 2 and 3, this bit contains the 8th data bit that was received. In Mode 1, if

SM2=0, RB8 is the Snap Bit that was received. In Mode 0, RB8 is not used

1TI

Transmit Interrupt 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

0RI

Receive Interrupt Flag. Set by hardware at the end of the 8th bit time in Mode 0, or

halfway through the Stop Bit in the other modes, in any serial reception (except for

SM2). Must be cleared by software

9202 Datasheet(PDF) 62 Page - STMicroelectronics