PIC18F23K20 Datasheet, PDF (161/420 Pages) Microchip Technology – 28/40/44-Pin Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology

15.4 PWM Mode
The PWM mode generates a Pulse-Width Modulated
signal on the CCP2 pin for the CCP module and the
P1A through P1D pins for the ECCP module. Hereafter
the modulated output pin will be referred to as the CCPx
pin. The duty cycle, period and resolution are
determined by the following registers:
• PR2
• T2CON
• CCPRxL
• CCPxCON
In Pulse-Width Modulation (PWM) mode, the CCP
module produces up to a 10-bit resolution PWM output
on the CCPx pin. Since the CCPx pin is multiplexed
with the PORT data latch, the TRIS for that pin must be
cleared to enable the CCPx pin output driver.
Note: Clearing the CCPxCON register will
relinquish CCPx control of the CCPx pin.
Figure 15-3 shows a simplified block diagram of PWM
operation.
Figure 15-4 shows a typical waveform of the PWM
signal.
For a step-by-step procedure on how to set up the CCP
module for PWM operation, see Section 15.4.7
“Setup for PWM Operation”.
FIGURE 15-3:
SIMPLIFIED PWM BLOCK
DIAGRAM
Duty Cycle Registers
CCPRxL
DCxB<1:0>
PIC18F2XK20/4XK20
The PWM output (Figure 15-4) has a time base
(period) and a time that the output stays high (duty
cycle).
FIGURE 15-4:
Period
CCP PWM OUTPUT
Pulse Width
TMR2 = 0
TMR2 = PR2
TMR2 = CCPRxL:DCxB<1:0>
CCPRxH⁽²⁾ (Slave)
Comparator
RQ
CCPx
TMR2
(1)
S
TRIS
Comparator
PR2
Clear Timer2,
toggle CCPx pin and
latch duty cycle
Note 1:
2:
The 8-bit timer TMR2 register is concatenated
with the 2-bit internal system clock (FOSC), or
2 bits of the prescaler, to create the 10-bit time
base.
In PWM mode, CCPRxH is a read-only register.
© 2007 Microchip Technology Inc.
Advance Information
DS41303B-page 159