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PIC16CR7X
DS21993C-page 58
2007 Microchip Technology Inc.
8.5.3
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 regis-
ter.
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 8-4:
EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (FOSC = 20 MHz)
TABLE 8-5:
REGISTERS ASSOCIATED WITH PWM AND TIMER2
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)
16
4
1
PR2 Value
0xFF
0x3F
0x1F
0x17
Maximum Resolution (bits)
10
8
7
5.5
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
TMR0IE
INTE
RBIE
TMR0IF
INTF
RBIF
0000 000x 0000 000u
0Ch
PIR1
PSPIF(1)
ADIF
RCIF
TXIF
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
11h
TMR2
Timer2 Module Register
0000 0000 0000 0000
92h
PR2
Timer2 Module 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
1Bh
CCPR2L
Capture/Compare/PWM Register 2 (LSB)
xxxx xxxx uuuu uuuu
1Ch
CCPR2H
Capture/Compare/PWM Register 2 (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 PWM and Timer2.
Note
1:
Bits PSPIE and PSPIF are reserved on the PIC16CR73/76; always maintain these bits clear.