UPSD3422_06 Datasheet, PDF (102/293 Pages) STMicroelectronics – Turbo Plus Series Fast Turbo 8032 MCU with USB and Programmable Logic

Serial UART interfaces
uPSD34xx
Table 48.
Bit 7
SM0
SCON1: serial port UART1 control register (SFR D8h, reset value 00h)
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
SM1
SM2
REN
TB8
RB8
TI
RI
Bit
Symbol
R/W
Definition
7
SM0
R,W Serial Mode Select, See Table 46 on page 100.
Important, notice bit order of SM0 and SM1.
[SM0:SM1] = 00b, Mode 0
6
SM1
R,W ^{[SM0:SM1] = 01b, Mode 1}
[SM0:SM1] = 10b, Mode 2
[SM0:SM1] = 11b, Mode 3
Serial Multiprocessor Communication Enable.
Mode 0: SM2 has no effect but should remain 0.
5
SM2
R,W ^{Mode 1: If SM2 = 0 then stop bit ignored. SM2 =1 then RI}
active if stop bit = 1.
Mode 2 and 3: Multiprocessor Comm Enable. If SM2=0, 9th
bit is ignored. If SM2=1, RI active when 9th bit = 1.
Receive Enable.
4
REN
R,W _{If REN=0, UART reception disabled. If REN=1, reception is}
enabled
3
TB8
R,W
TB8 is assigned to the 9th transmission bit in Mode 2 and 3.
Not used in Mode 0 and 1.
Mode 0: RB8 is not used.
Mode 1: If SM2 = 0, the RB8 is the level of the received stop
2
RB8
R,W bit.
Mode 2 and 3: RB8 is the 9th data bit that was received in
Mode 2 and 3.
Transmit Interrupt flag.
1
TI
R,W ^{Causes interrupt at end of 8th bit time when transmitting in}
Mode 0, or at beginning of stop bit transmission in other
modes. Must clear flag with firmware.
Receive Interrupt flag.
0
RI
R,W ^{Causes interrupt at end of 8th bit time when receiving in Mode}
0, or halfway through stop bit reception in other modes (see
SM2 for exception). Must clear this flag with firmware.
21.3
UART baud rates
The baud rate in Mode 0 is fixed:
Mode 0 Baud Rate = f_OSC / 12
The baud rate in Mode 2 depends on the value of the bit SMOD in the SFR named PCON. If
SMOD = 0 (default value), the baud rate is 1/64 the oscillator frequency, f_OSC. If SMOD = 1,
the baud rate is 1/32 the oscillator frequency.
Mode 2 Baud Rate = (2^SMOD / 64) x f_OSC
Baud rates in Modes 1 and 3 are determined by the Timer 1 or Timer 2 overflow rate.
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