PIC16F87 datasheet(85/230 Pages) MICROCHIP

85 / 230 page

 2002-2013 Microchip Technology Inc.

DS30487D-page 85

PIC16F87/88

The maximum PWM resolution (bits) for a given PWM

frequency is given by the following formula.

EQUATION 9-3:

9.3.3

SETUP 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

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

TRISB<x> bit.

Set the TMR2 prescale value and enable Timer2

by writing to T2CON.

Configure the CCP1 module for PWM operation.

TABLE 9-3:

EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 20 MHz

TABLE 9-4:

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

Resolution

Note:

The TRISB bit (0 or 3) is dependant upon

the

setting

configuration

bit

(CCPMX).

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)

6.6

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

INT0IE

RBIE

TMR0IF

INT0IF

RBIF

0000 000x 0000 000u

0Ch

PIR1

—

ADIF(1)

RCIF

TXIF

SSPIF

CCP1IF

TMR2IF

TMR1IF

-000 0000 -000 0000

8Ch

PIE1

—

ADIE(1)

RCIE

TXIE

SSPIE

CCP1IE

TMR2IE

TMR1IE

-000 0000 -000 0000

86h

TRISB

PORTB Data Direction Register

1111 1111 1111 1111

11h

TMR2

Timer2 Module Register

0000 0000 0000 0000

92h

PR2

Timer2 Period Register

1111 1111 1111 1111

12h

T2CON

—

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

15h

CCPR1L

Capture/Compare/PWM Register 1 (LSB)

xxxx xxxx uuuu uuuu

16h

CCPR1H

Capture/Compare/PWM Register 1 (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.

Note

This bit is only implemented on the PIC16F88. The bit will read ‘0’ on the PIC16F87.

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