PIC18F6585 Datasheet, PDF (176/496 Pages) Microchip Technology – 64/68/80-Pin High-Performance, 64-Kbyte Enhanced Flash Microcontrollers with ECAN Module

PIC18F6585/8585/6680/8680
The maximum PWM resolution (bits) for a given PWM
frequency is given by the following equation.
EQUATION 15-3:
PWM Resolution (max)
=
log


F--F--P^-O--W^{--S---CM---}
----------------------------- bits
log (2)
Note:
If the PWM duty cycle value is longer than
the PWM period, the CCP1 pin will not be
cleared.
15.4.3 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
CCPRxL register and CCPxCON<5:4> bits.
3. Make the CCPx pin an output by clearing
corresponding TRIS bit.
4. Set the TMR2 prescale value and enable Timer2
by writing to T2CON.
5. Configure the CCPx module for PWM operation.
TABLE 15-4: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz
PWM Frequency
2.44 kHz 9.76 kHz 39.06 kHz 156.3 kHz 312.5 kHz
Timer Prescaler (1, 4, 16)
PR2 Value
Maximum Resolution (bits)
16
4
1
1
1
0FFh
0FFh
0FFh
3Fh
1Fh
10
10
10
8
7
416.6 kHz
1
17h
5.5
TABLE 15-5: REGISTERS ASSOCIATED WITH PWM AND TIMER2
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
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 0000 000x 0000 000u
PIR1
PSPIF
ADIF
RCIF
TXIF
SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 0000 0000
PIE1
PSPIE
ADIE
RCIE
TXIE
SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 0000 0000
IPR1
PSPIP
ADIP
RCIP
TXIP
SSPIP CCP1IP TMR2IP TMR1IP 1111 1111 1111 1111
TRISC PORTC Data Direction Register
1111 1111 1111 1111
TMR2 Timer2 Module Register
0000 0000 0000 0000
PR2
Timer2 Module Period Register
1111 1111 1111 1111
T2CON
—
TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 -000 0000
CCPR1L Capture/Compare/PWM Register 1 (LSB)
xxxx xxxx uuuu uuuu
CCPR1H Capture/Compare/PWM Register 1 (MSB)
xxxx xxxx uuuu uuuu
CCP1CON P1M1
P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 0000 0000 0000 0000
CCPR2L Capture/Compare/PWM Register 2 (LSB)
xxxx xxxx uuuu uuuu
CCPR2H Capture/Compare/PWM Register 2 (MSB)
xxxx xxxx uuuu uuuu
CCP2CON
—
—
DC2B1 DC2B0 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.
DS30491C-page 174
 2004 Microchip Technology Inc.