UPSD3354DV-40U6 Datasheet, PDF (110/272 Pages) STMicroelectronics – fast 8032 MCU with programmable logic

Serial UART interfaces
UPSD33xx
Table 66.
Bit
1
0
SCON1 register bit definition (continued)
Symbol
R/W
Definition
Transmit Interrupt flag.
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.
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:
Obsolete ^{Product(s) - Obsolete Product(s) 21.3.1}
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.
Using Timer 1 to generate baud rates
When Timer 1 is used as the baud rate generator (bits RCLK = 0, TCLK = 0), the baud rates
in modes 1 and 3 are determined by the Timer 1 overflow rate and the value of SMOD as
follows:
Mode 1,3 Baud Rate =
(2^SMOD / 32) x (Timer 1 overflow rate)
The Timer 1 Interrupt should be disabled in this application. The Timer itself can be
configured for either “timer” or “counter” operation, and in any of its 3 running modes. In the
most typical applications, it is configured for “timer” operation, in the Auto-reload mode (high
nibble of the SFR TMOD = 0010B). In that case the baud rate is given by the formula:
Mode 1,3 Baud Rate =
(2^SMOD / 32) x (f_OSC / (12 x [256 – (TH1)]))
Table 67 on page 111 lists various commonly used baud rates and how they can be
obtained from Timer 1.
110/272
Doc ID 9685 Rev 7