PIC16F7X
3. Make the CCP1 pin an output by clearing the
TRISC<2> bit.
8.5.3
SETUP FOR PWM OPERATION
The following steps should be taken when configuring
the CCP module for PWM operation:
4. Set the TMR2 prescale value and enable Timer2
by writing to T2CON.
1. Set the PWM period by writing to the PR2 register.
5. Configure the CCP1 module for PWM operation.
2. Set the PWM duty cycle by writing to the
CCPR1L register and CCP1CON<5:4> bits.
TABLE 8-4:
EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (FOSC = 20 MHz)
PWM Frequency
1.22 kHz
4.88 kHz
19.53 kHz
78.12 kHz
156.3 kHz
208.3 kHz
Timer Prescale (1, 4, 16)
PR2 Value
16
0xFF
10
4
1
1
0x3F
8
1
0x1F
7
1
0xFF
10
0xFF
10
0x17
5.5
Maximum Resolution (bits)
TABLE 8-5:
REGISTERS ASSOCIATED WITH PWM AND TIMER2
Value on:
POR,
BOR
Value on
all other
RESETS
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0Bh,8Bh, INTCON
10Bh,18Bh
GIE
PEIE
TMR0IE
INTE
RBIE
TMR0IF
INTF
RBIF
0000 000x 0000 000u
(1)
0Ch
0Dh
8Ch
8Dh
87h
11h
92h
12h
15h
16h
17h
1Bh
1Ch
1Dh
PIR1
PSPIF
—
ADIF
—
RCIF
—
TXIF
—
SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 0000 0000
CCP2IF ---- ---0 ---- ---0
SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 0000 0000
PIR2
—
—
—
(1)
PIE1
PSPIE
—
ADIE
—
RCIE
—
TXIE
—
PIE2
—
—
—
CCP2IE ---- ---0 ---- ---0
1111 1111 1111 1111
0000 0000 0000 0000
1111 1111 1111 1111
TRISC
TMR2
PR2
PORTC Data Direction Register
Timer2 Module Register
Timer2 Module Period Register
T2CON
—
TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 -000 0000
CCPR1L Capture/Compare/PWM Register1 (LSB)
CCPR1H Capture/Compare/PWM Register1 (MSB)
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
CCP1CON
—
—
CCP1X CCP1Y CCP1M3 CCP1M2 CCP1M1 CCP1M0 --00 0000 --00 0000
CCPR2L Capture/Compare/PWM Register2 (LSB)
CCPR2H Capture/Compare/PWM Register2 (MSB)
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
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 PWM and Timer2.
Note 1: Bits PSPIE and PSPIF are reserved on the PIC16F73/76; always maintain these bits clear.
DS30325B-page 58
2002 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
