PIC16F72SLASHML datasheet(44/136 Pages) MICROCHIP

44 / 136 page

PIC16F72

DS39597B-page 42

 2002 Microchip Technology Inc.

Maximum PWM resolution (bits) for a given PWM

frequency is calculated using Equation 8-3.

EQUATION 8-3:

PWM MAX RESOLUTION

For a sample PWM period and duty cycle calculation,

see the PICmicro™ Mid-Range MCU Reference

Manual (DS33023).

8.3.3

SET-UP FOR PWM OPERATION

The following steps should be taken when configuring

the CCP module for PWM operation:

Set the PWM period by writing to the PR2 register.

Set the PWM duty cycle by writing to the

CCPR1L register and CCP1CON<5:4> bits.

Make the CCP1 pin an output by clearing the

TRISC<2> bit.

Set the TMR2 prescale value and enable Timer2

by writing to T2CON.

Configure the CCP1 module for PWM operation.

TABLE 8-3:

EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 20 MHz

TABLE 8-4:

REGISTERS ASSOCIATED WITH PWM AND TIMER2

Note:

If the PWM duty cycle value is longer than

the PWM period, the CCP1 pin will not be

cleared.

log (

FPWM

log(2)

FOSC

)

bits

PWM Maximum Resolution =

PWM Frequency

1.22 kHz

4.88 kHz

19.53 kHz

78.12 kHz

156.3 kHz

208.3 kHz

Timer Prescaler (1, 4, 16)

PR2 Value

0xFF

0x3F

0x1F

0x17

Maximum Resolution (bits)

5.5

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Value on

POR, BOR

Value on

all other

RESETS

0Bh,8Bh

10Bh,18Bh

INTCON

GIE

PEIE

TMR0IE

INTE

RBIE

TMR0IF

INTF

RBIF

0000 000x 0000 000u

0Ch

PIR1

—

ADIF

—

SSPIF

CCP1IF

TMR2IF

TMR1IF -0-- 0000 0000 0000

8Ch

PIE1

—

ADIE

—

SSPIE

CCP1IE

TMR2IE

TMR1IE -0-- 0000 0000 0000

87h

TRISC

PORTC Data Direction Register

1111 1111 1111 1111

11h

TMR2

Timer2 Module Register

0000 0000 0000 0000

92h

PR2

Timer2 Module Period Register

1111 1111 1111 1111

12h

T2CON

—

TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 -000 0000

15h

CCPR1L

Capture/Compare/PWM Register1 (LSB)

xxxx xxxx uuuu uuuu

16h

CCPR1H

Capture/Compare/PWM Register1 (MSB)

xxxx xxxx uuuu uuuu

17h

CCP1CON

—

CCP1X

CCP1Y

CCP1M3 CCP1M2 CCP1M1 CCP1M0 --00 0000 --00 0000

Legend:

= unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used by PWM and Timer2.

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