PIC18LF252-ISP Datasheet, PDF(125/332 Page) Microchip Technology – High-Performance, Enhanced Flash Microcontrollers with 10-Bit A/D

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PIC18LF252-ISP Datasheet, PDF (125/332 Pages) Microchip Technology – High-Performance, Enhanced Flash Microcontrollers with 10-Bit A/D

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PIC18FXX2

14.5.3 SETUP FOR PWM OPERATION

The following steps should be taken when configuring

the CCP module for PWM operation:

1. Set the PWM period by writing to the PR2 register.

2. Set the PWM duty cycle by writing to the

CCPR1L register and CCP1CON<5:4> bits.

3. Make the CCP1 pin an output by clearing the

TRISC<2> bit.

4. Set the TMR2 prescale value and enable Timer2

by writing to T2CON.

5. Configure the CCP1 module for PWM operation.

TABLE 14-4: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz

PWM Frequency

Timer Prescaler (1, 4, 16)

PR2 Value

Maximum Resolution (bits)

2.44 kHz

16

0xFF

14

9.77 kHz

4

0xFF

12

39.06 kHz

1

0xFF

10

156.25 kHz 312.50 kHz 416.67 kHz

1

0x3F

8

1

0x1F

7

1

0x17

6.58

TABLE 14-5: REGISTERS ASSOCIATED WITH PWM AND TIMER2

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

INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE

RBIE TMR0IF INT0IF

RBIF 0000 000x 0000 000u

PIR1

PIE1

PSPIF(1)

PSPIE(1)

ADIF

ADIE

RCIF

RCIE

TXIF

TXIE

SSPIF

SSPIE

CCP1IF TMR2IF TMR1IF 0000 0000 0000 0000

CCP1IE TMR2IE TMR1IE 0000 0000 0000 0000

IPR1

PSPIP(1) ADIP

RCIP

TXIP

SSPIP CCP1IP TMR2IP TMR1IP 0000 0000 0000 0000

TRISC PORTC Data Direction Register

1111 1111 1111 1111

TMR2

Timer2 Module Register

0000 0000 0000 0000

PR2

Timer2 Module Period Register

1111 1111 1111 1111

T2CON

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

CCPR1L Capture/Compare/PWM Register1 (LSB)

xxxx xxxx uuuu uuuu

CCPR1H Capture/Compare/PWM Register1 (MSB)

xxxx xxxx uuuu uuuu

CCP1CON â

â

DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 --00 0000 --00 0000

CCPR2L Capture/Compare/PWM Register2 (LSB)

xxxx xxxx uuuu uuuu

CCPR2H Capture/Compare/PWM Register2 (MSB)

xxxx xxxx uuuu uuuu

CCP2CON â

â

DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 --00 0000 --00 0000

Legend: x = unknown, u = unchanged, - = unimplemented, read as '0'. Shaded cells are not used by PWM and Timer2.

Note 1: The PSPIF, PSPIE and PSPIP bits are reserved on the PIC18F2X2 devices; always maintain these bits clear.

Â© 2006 Microchip Technology Inc.

DS39564C-page 123

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