Datasheet

 2000-2013 Microchip Technology Inc. DS30569C-page 59
PIC16F870/871
8.4.3 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 8-2: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 20 MHz
TABLE 8-3: REGISTERS ASSOCIATED WITH CAPTURE, COMPARE, AND TIMER1
PWM Frequency 1.22 kHz 4.88 kHz 19.53 kHz 78.12kHz 156.3 kHz 208.3 kHz
Timer Prescaler (1, 4, 16) 16 4 1 1 1 1
PR2 Value 0xFFh 0xFFh 0xFFh 0x3Fh 0x1Fh 0x17h
Maximum Resolution (bits) 10 10 10 8 7 6.5
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
T0IE INTE RBIE T0IF INTF RBIF 0000 000x 0000 000u
0Ch PIR1
PSPIF
(1)
ADIF RCIF TXIF — CCP1IF TMR2IF TMR1IF 0000 -000 0000 -000
8Ch PIE1
PSPIE
(1)
ADIE RCIE TXIE —CCP1IETMR2IE TMR1IE 0000 -000 0000 -000
87h TRISC PORTC Data Direction Register 1111 1111 1111 1111
0Eh TMR1L Holding Register for the Least Significant Byte of the 16-bit TMR1 Register xxxx xxxx uuuu uuuu
0Fh TMR1H Holding Register for the Most Significant Byte of the 16-bit TMR1 Register xxxx xxxx uuuu uuuu
10h T1CON
— — T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON --00 0000 --uu uuuu
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: x = unknown, u = unchanged, - = unimplemented, read as '0'. Shaded cells are not used by Capture and Timer1.
Note 1: The PSP is not implemented on the PIC16F870; always maintain these bits clear.