Download C868 8 - SELF8051

C868
On-Chip Peripheral Components
T2CON) must be set. To enable the baud generator for receive, bit RCLK (bit 5 of
special function register T2CON) must be set.
With the timer 2 as clock source for the serial port in mode 1 and 3, the baud rate can be
determined as follows:
Mode 1, 3 baud rate =
2SMOD
32
x (timer 2 overflow rate)
Timer 2 overflow rate = system frequency / 2x(216 – RC2)
with RC2 = RC2H.7..0, RC2L.7..0 and timer2
count direction is set to up.
Using Timer 1 to Generate Baud Rates
In modes 1 and 3 of the serial interface timer 1 can also be used for generating baud
rates. Then the baud rate is determined by the timer 1 overflow rate and the value of
SMOD as follows:
Mode 1, 3 baud rate =
2SMOD
32
x (timer 1 overflow rate)
The timer 1 interrupt is usually disabled in this application. Timer 1 itself can be
configured for either "timer" or "counter" operation, and in any of its operating modes. In
most typical applications, it is configured for "timer" operation in the auto-reload mode
(high nibble of TMOD = 0010B). In this case the baud rate is given by the formula:
2SMOD x
system frequency
Mode 1, 3 baud rate =
32 x 12 x (256 – (TH1))
Very low baud rates can be achieved with timer 1 if leaving the timer 1 interrupt enabled,
configuring the timer to run as 16-bit timer (high nibble of TMOD = 0001B), and using the
timer 1 interrupt for a 16-bit software reload.
User’s Manual
4-106
V 1.0, 2003-01