AT89LP213 datasheet(40/90 Pages) ATMEL

40 / 90 page

3538A–MICRO–7/06

AT89LP213/214 [Preliminary]

17.2

Baud Rates

The baud rate in Mode 0 is fixed as shown in the following equation:

The baud rate in Mode 2 depends on the value of the SMOD1 bit in Special Function Register

PCON.7. If SMOD1 = 0 (the value on reset), the baud rate is 1/32 of the oscillator frequency. If

SMOD1 = 1, the baud rate is 1/16 of the oscillator frequency, as shown in the following equation:

17.2.1

Using Timer 1 to Generate Baud Rates

The Timer 1 overflow rate determines the baud rates in Modes 1 and 3. When Timer 1 is the

baud rate generator, the baud rates are determined by the Timer 1 overflow rate and the value

of SMOD1 according to the following equation:

The Timer 1 interrupt should be disabled in this application. The Timer itself can be configured

for either timer or counter operation in any of its 3 running modes. In the most typical applica-

tions, it is configured for timer operation in auto-reload mode (high nibble of TMOD = 0010B). In

this case, the baud rate is given by the following formula:

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 17-2 lists commonly used baud rates and how they can be obtained from Timer 1.

Mode 0 Baud Rate

Oscillator Frequency

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

Mode 2 Baud Rate

SMOD1

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

(Oscillator Frequency)

Table 17-2.

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: 375K

62.5K

F4H

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

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

(Timer 1 Overflow Rate)

Modes 1, 3

Baud Rate

SMOD1

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

Oscillator Frequency

256

TH1

()

–

[]

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

TPS 1

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

Modes 1, 3

Baud Rate

SMOD1

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

Oscillator Frequency

256

RH1,RL1

()

–

[]

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

TPS 1

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

AT89LP213 Datasheet(PDF) 40 Page - ATMEL Corporation

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