PIC16C62B/72A
7.3.3
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 on-time 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 7-4
EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 20 MHz
PWM Frequency
1.22 kHz 4.88 kHz 19.53 kHz 78.12 kHz 156.3 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 7-5
REGISTERS ASSOCIATED WITH PWM AND TIMER2
Value on
Value on
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
POR,
BOR
all other
resets
0Bh,8Bh
0Ch
8Ch
87h
INTCON
PIR1
GIE
—
PEIE
ADIF
ADIE
T0IE
—
INTE
—
RBIE
SSPIF
SSPIE
T0IF
INTF
RBIF
0000 000x 0000 000u
CCP1IF TMR2IF TMR1IF -0-- 0000 -0-- 0000
CCP1IE TMR2IE TMR1IE -0-- 0000 -0-- 0000
1111 1111 1111 1111
PIE1
—
—
—
TRISC
TMR2
PORTC Data Direction Register
Timer2 module’s register
11h
0000 0000 0000 0000
92h
PR2
Timer2 module’s period register
1111 1111 1111 1111
12h
T2CON
CCPR1L
CCPR1H
CCP1CON
—
TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 -000 0000
15h
Capture/Compare/PWM register1 (LSB)
Capture/Compare/PWM register1 (MSB)
xxxx xxxx uuuu uuuu
xxxx xxxx uuuu uuuu
16h
17h
—
—
CCP1X
CCP1Y CCP1M3 CCP1M2 CCP1M1 CCP1M0 --00 0000 --00 0000
Legend: x= unknown, u= unchanged, -= unimplemented read as '0'. Shaded cells are not used by PWM and Timer2.
1999 Microchip Technology Inc.
Preliminary
DS35008B-page 37
MICROCHIP [ MICROCHIP ]
