PIC16F87X Datasheet, PDF (64/218 Pages) Microchip Technology – 28/40-pin 8-Bit CMOS FLASH Microcontrollers

PIC16F87X
8.3.3 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 8-3: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 20 MHz
PWM Frequency
Timer Prescaler (1, 4, 16)
PR2 Value
Maximum Resolution (bits)
1.22 kHz
16
0xFFh
10
4.88 kHz
4
0xFFh
10
19.53 kHz
1
0xFFh
10
78.12kHz
1
0x3Fh
8
156.3 kHz
1
0x1Fh
7
208.3 kHz
1
0x17h
5.5
TABLE 8-4: REGISTERS ASSOCIATED WITH CAPTURE, COMPARE, AND TIMER1
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, INTCON
10Bh, 18Bh
0Ch
PIR1
GIE PEIE
PSPIF⁽¹⁾ ADIF
T0IE
RCIF
INTE
TXIF
RBIE
T0IF
INTF RBIF 0000 000x 0000 000u
SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 0000 0000
0Dh
PIR2
—
—
—
—
—
—
— CCP2IF ---- ---0 ---- ---0
8Ch
PIE1
PSPIE⁽¹⁾ ADIE RCIE
TXIE
SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 0000 0000
8Dh
PIE2
—
—
—
—
—
—
— CCP2IE ---- ---0 ---- ---0
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
1Bh
CCPR2L Capture/Compare/PWM Register2 (LSB)
xxxx xxxx uuuu uuuu
1Ch
CCPR2H Capture/Compare/PWM Register2 (MSB)
xxxx xxxx uuuu uuuu
1Dh
CCP2CON —
— CCP2X CCP2Y CCP2M3 CCP2M2 CCP2M1 CCP2M0 --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 PIC16F873/876; always maintain these bits clear.
DS30292C-page 62
 2001 Microchip Technology Inc.