PIC18F24J11 MICROCHIP [Microchip Technology], PIC18F24J11 Datasheet - Page 252

• Manufacturer Part Number: PIC18F24J11
• Description: 28/44-Pin, Low-Power, High-Performance USB Microcontrollers with nanoWatt XLP Technology
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F46J11 FAMILY
18.4
In Pulse-Width Modulation (PWM) mode, the CCPx pin
produces up to a 10-bit resolution PWM output.
Figure 18-3
CCP module in PWM mode.
For a step-by-step procedure on how to set up a CCP
module for PWM operation, see
“Setup for PWM
FIGURE 18-3:
A PWM output
and a time that the output stays high (duty cycle).
The frequency of the PWM is the inverse of the
period (1/period).
FIGURE 18-4:
DS39932D-page 252
Note:
Note 1:
Latch
Duty Cycle
TMRx = PRx
Set CCPx pin
Reset
Match
TMR2 (TMR4) = PR2 (TMR4)
PWM Mode
The two LSbs of the Duty Cycle register are held by a
2-bit latch that is part of the module’s hardware. It is
physically separate from the CCPRx registers.
Duty Cycle Register
Clearing the CCPxCON register will force
the output latch (depending on device
configuration) to the default low level. This
is not the LATx data latch.
Duty Cycle
shows a simplified block diagram of the
9
Comparator
CCPRxL
CCPRxH
Comparator
(Figure
TMRx
PRx
Period
Operation”.
TMR2 (TMR4) = Duty Cycle
SIMPLIFIED PWM BLOCK
DIAGRAM
PWM OUTPUT
18-4) has a time base (period)
(1)
0
TMR2 (TMR4) = PR2 (PR4)
CCPxCON<5:4>
2 LSbs latched
from Q clocks
S
R
Q
Output Enable
Section 18.4.3
TRIS
CCPx
pin
18.4.1
The PWM period is specified by writing to the PR2
(PR4) register. The PWM period can be calculated
using
EQUATION 18-1:
PWM frequency is defined as 1/[PWM period].
When TMR2 (TMR4) is equal to PR2 (PR4), the
following three events occur on the next increment
cycle:
• TMR2 (TMR4) is cleared
• The CCPx pin is set (exception: if PWM duty
• The PWM duty cycle is latched from CCPRxL into
18.4.2
The PWM duty cycle is specified by writing to the
CCPRxL register and to the CCPxCON<5:4> bits. Up
to 10-bit resolution is available. The CCPRxL contains
the eight MSbs and the CCPxCON<5:4> contains the
two LSbs. This 10-bit value is represented by
CCPRxL:CCPxCON<5:4>.
calculate the PWM duty cycle in time.
EQUATION 18-2:
CCPRxL and CCPxCON<5:4> can be written to at any
time, but the duty cycle value is not latched into
CCPRxH until after a match between PR2 (PR4) and
TMR2 (TMR4) occurs (i.e., the period is complete). In
PWM mode, CCPRxH is a read-only register.
cycle = 0%, the CCPx pin will not be set)
CCPRxH
Note:
PWM Duty Cycle = (CCPR
Equation
PWM Period = [(PR2) + 1] • 4 • T
PWM PERIOD
The Timer2 and Timer 4 postscalers (see
Section 14.0 “Timer2 Module”
Section 16.0 “Timer4
used in the determination of the PWM
frequency. The postscaler could be used
to have a servo update rate at a different
frequency than the PWM output.
PWM DUTY CYCLE
18-1:
T
OSC
(TMR2 Prescale Value)
 2011 Microchip Technology Inc.
• (TMR2 Prescale Value)
Equation 18-2
X
L:CCP
Module”) are not
X
CON<5:4>) •
OSC
is used to
•
and