PIC18CXX2
13.5.3 SET-UP 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 13-4: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz
PWM Frequency
2.44 kHz 9.76 kHz 19.53 kHz 39.06 kHz 78.12 kHz 208.3 kHz
Timer Prescaler (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 13-5: REGISTERS ASSOCIATED WITH PWM AND TIMER2
Value on
Value on
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
POR,
BOR
all other
resets
INTCON
GIE/
PEIE/
TMR0IE
INT0IE
RBIE
TMR0IF
INT0IF
RBIF
0000 000x
0000 000u
GIEH
GIEL
ADIF
ADIE
ADIP
PIR1
PSPIF (1)
PSPIE(1)
PSPIP(1)
RCIF
RCIE
RCIP
TXIF
TXIE
TXIP
SSPIF
SSPIE
SSPIP
CCP1IF
CCP1IE
CCP1IP
TMR2IF
TMR2IE
TMR2IP
TMR1IF
TMR1IE
TMR1IP
0000 0000
0000 0000
0000 0000
1111 1111
0000 0000
1111 1111
-000 0000
xxxx xxxx
xxxx xxxx
--00 0000
xxxx xxxx
xxxx xxxx
--00 0000
0000 0000
0000 0000
0000 0000
1111 1111
0000 0000
1111 1111
-000 0000
uuuu uuuu
uuuu uuuu
--00 0000
uuuu uuuu
uuuu uuuu
--00 0000
PIE1
IPR1
TRISC
PORTC Data Direction Register
Timer2 module’s register
TMR2
PR2
Timer2 module’s period register
T2CON
CCPR1L
CCPR1H
CCP1CON
CCPR2L
CCPR2H
CCP2CON
—
TOUTPS3
TOUTPS2
TOUTPS1
DC1B0
TOUTPS0
CCP1M3
CCP2M3
TMR2ON
CCP1M2
CCP2M2
T2CKPS1
CCP1M1
CCP2M1
T2CKPS0
CCP1M0
CCP2M0
Capture/Compare/PWM register1 (LSB)
Capture/Compare/PWM register1 (MSB)
—
—
DC1B1
Capture/Compare/PWM register2 (LSB)
Capture/Compare/PWM register2 (MSB)
—
—
DC2B1
DC2B0
Legend: x= unknown, u= unchanged, — = unimplemented read as ’0’.
Shaded cells are not used by PWM and Timer2.
Note 1: The PSPIF, PSPIE and PSPIP bits are reserved on the PIC18C2X2 devices. Always maintain these bits clear.
DS39026B-page 116
Preliminary
7/99 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
