AT89LP6440 datasheet(56/194 Pages) ATMEL

56 / 194 page

3706A–MICRO–9/09

AT89LP6440 - Preliminary

11.5.1

Mode 0 – 8-bit PWM with 8-bit Logarithmic Prescaler

In Mode 0, TLx acts as a logarithmic prescaler driving 8-bit counter THx (see Figure 11-6). The

PSCx bits in TCONB control the prescaler value. On THx overflow, the duty cycle value in RHx

is transferred to OCRx and the output pin is set high. When the count in THx matches OCRx, the

output pin is cleared low. The following formulas give the output frequency and duty cycle for

Timer 0 in PWM Mode 0. Timer 1 in PWM Mode 0 is identical to Timer 0.

Figure 11-6. Timer/Counter 1 PWM Mode 0

11.5.2

Mode 1 – 8-bit PWM with 8-bit Linear Prescaler

In Mode 1, TLx provides linear prescaling with an 8-bit auto-reload from RLx (see Figure 11-7 on

page 57). On TLx overflow, TLx is loaded with the value of RLx. THx acts as an 8-bit counter. On

THx overflow, the duty cycle value in RHx is transferred to OCRx and the output pin is set high.

When the count in THx matches OCRx, the output pin is cleared low. The following formulas

give the output frequency and duty cycle for Timer 0 in PWM Mode 1. Timer 1 in PWM Mode 1 is

identical to Timer 0.

11.5.3

Mode 2 – 8-bit Frequency Generator

Timer 0 in PWM Mode 2 functions as an 8-bit Auto-Reload timer, the same as normal Mode 2,

with the exception that the output pin T0 is toggled at every TL0 overflow (see Figure 11-8 and

Figure 11-9 on page 57). Timer 1 in PWM Mode 2 is identical to Timer 0. PWM Mode 2 can be

used to output a square wave of varying frequency. THx acts as an 8-bit counter. The following

formula gives the output frequency for Timer 0 in PWM Mode 2.

Mode 0:

out

Oscillator Frequency

256

PSC0

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

TPS

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

Duty Cycle %

100

RH0

256

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

OSC

TR1

GATE1

INT1 Pin

TL1

(8 Bits)

Control

PSC1

TH1

(8 Bits)

OCR1

RH1

(8 Bits)

÷TPS

Mode 1:

out

Oscillator Frequency

256

RL0

–

()

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

TPS

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

Duty Cycle %

100

RH0

256

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

Mode 2:

out

Oscillator Frequency

2256

TH0

–

()

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

TPS

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

AT89LP6440 Datasheet(PDF) 56 Page - ATMEL Corporation

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