AT89LP428 datasheet(80/149 Pages) ATMEL

80 / 149 page

3654A–MICRO–8/09

AT89LP428/828

Programmers can achieve very low baud rates with Timer 1 by configuring the Timer to run as a

16-bit auto-reload timer (high nibble of TMOD = 0001B). In this case, the baud rate is given by

the following formula.

Table 16-2 lists commonly used baud rates and how they can be obtained from Timer 1.

16.2.2

Using Timer 2 to Generate Baud Rates

Timer 2 is selected as the baud rate generator by setting TCLK and/or RCLK in T2CON. Under

these conditions, the baud rates for transmit and receive can be simultaneously different by

using Timer 1 for transmit and Timer 2 for receive, or vice versa. The baud rate generator mode

is similar to the auto-reload mode, in that a rollover causes the Timer 2 registers to be reloaded

with the 16-bit value in registers RCAP2H and RCAP2L, which are preset by software. In this

case, the baud rates in Modes 1 and 3 are determined by Timer 2’s overflow rate according to

the following equation:.

Table 16-3 lists commonly used baud rates and how they can be obtained from Timer 2.

Table 16-2.

Commonly Used Baud Rates Generated by Timer 1 (TPS = 0000B)

Baud Rate

OSC (MHz)

SMOD1

Timer 1

C/T

Mode

Reload Value

Mode 0: 1 MHz

Mode 2: 750K

62.5K

F4H

38.4K

11.059

F7H

19.2K

11.059

DCH

9.6K

11.059

DCH

4.8K

11.059

B8H

2.4K

11.059

70H

1.2K

11.059

FEE0H

137.5

11.986

F55CH

110

F958H

110

F304H

Modes 1, 3

Baud Rate

SMOD1

--------------------

Oscillator Frequency

65536

RH1,RL1

()

–

[]

--------------------------------------------------------

TPS

---------------------

Modes 1 and 3

Baud Rate

------

Oscillator Frequency

65536

RCAP2H,RCAP2L

()

–

[]

---------------------------------------------------------------------------------

TPS

---------------------

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