Rainbow-electronics AT89LP216 Manual do Utilizador descarregar pdf (Página 40)

3621A–MICRO–6/06

AT89LP216 [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.

Mode 0 Baud Rate

Oscillator Frequency

------------------------------------------------------ -=

Mode 2 Baud Rate

SMOD1

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

(Oscillator Frequency)×=

Modes 1, 3

Baud Rate

SMOD1

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

(Timer 1 Overflow Rate)×=

Modes 1, 3

Baud Rate

SMOD1

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

Oscillator Frequency

256 TH1()–[]

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

TPS

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

××=

Modes 1, 3

Baud Rate

SMOD1

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

Oscillator Frequency

256

H1,RL1()–[]

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

TPS

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

×=

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 89 90

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