PIC18FXX20
16.4.3
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 16-3: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz
PWM Frequency
2.44 kHz
9.77 kHz
39.06 kHz 156.25 kHz 312.50 kHz 416.67 kHz
Timer Prescaler (1, 4, 16)
PR2 Value
Maximum Resolution (bits)
16
FFh
14
4
FFh
12
1
FFh
10
1
3Fh
8
1
1Fh
7
1
17h
6.58
TABLE 16-4: REGISTERS ASSOCIATED WITH PWM, TIMER2 AND TIMER4
Value on
Value on
POR, BOR
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
all other
RESETS
INTCON
RCON
PIR1
PIE1
IPR1
PIR2
PIE2
IPR2
PIR3
PIE3
IPR3
TMR2
PR2
GIE/GIEH PEIE/GIEL TMR0IE
INT0IE
RI
RBIE
TO
TMR0IF
PD
INT0IF
POR
RBIF
BOR
0000 00000000 0000
IPEN
PSPIF
PSPIE
PSPIP
—
—
—
—
—
—
ADIF
ADIE
ADIP
CMIE
CMIF
CMIP
—
—
RCIF
RCIE
RCIP
—
—
—
RC2IF
RC2IE
RC2IP
0--1 11qq0--q qquu
TXIF
TXIE
TXIP
EEIE
EEIF
EEIP
TX2IF
TX2IE
TX2IP
SSPIF
SSPIE
SSPIP
BCLIF
BCLIE
BCLIP
TMR4IF
TMR4IE
TMR4IP
CCP1IF TMR2IF TMR1IF 0000 00000000 0000
CCP1IE TMR2IE TMR1IE 0000 00000000 0000
CCP1IP TMR2IP TMR1IP 0111 11110111 1111
LVDIF
LVDIE
LVDIP
CCP5IF CCP4IF CCP3IF --00 0000--00 0000
CCP5IE CCP4IE CCP3IE --00 0000--00 0000
CCP5IP CCP4IP CCP3IP --11 1111--11 1111
0000 00000000 0000
TMR3IF CCP2IF -0-0 0000---0 0000
TMR3IE CCP2IE -0-0 0000---0 0000
TMR3IP CCP2IP -1-1 1111---1 1111
—
—
—
Timer2 Module Register
Timer2 Module Period Register
1111 11111111 1111
T2CON
T3CON
TMR4
PR4
—
RD16
T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000-000 0000
T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 0000 0000uuuu uuuu
Timer4 Register
Timer4 Period Register
0000 0000uuuu uuuu
1111 1111uuuu uuuu
T4CON
CCPRxL
CCPRxH
—
T4OUTPS3 T4OUTPS2 T4OUTPS1 T4OUTPS0 TMR4ON T4CKPS1 T4CKPS0 -000 0000uuuu uuuu
(1)
Capture/Compare/PWM Register x (LSB)
Capture/Compare/PWM Register x (MSB)
xxxx xxxxuuuu uuuu
(1)
(1)
xxxx xxxxuuuu uuuu
CCPxCON
—
—
DCxB1
DCxB0
CCPxM3 CCPxM2 CCPxM1 CCPxM0 --00 0000--00 0000
Legend: x= unknown, u= unchanged, - = unimplemented, read as '0'. Shaded cells are not used by PWM, Timer2, or Timer4.
Note 1: Generic term for all of the identical registers of this name for all CCP modules, where ‘x’ identifies the individual module
(CCP1 through CCP5). Bit assignments and RESET values for all registers of the same generic name are identical.
2003 Microchip Technology Inc.
Advance Information
DS39609A-page 155
MICROCHIP [ MICROCHIP ]
