PIC18F6410ESLASHPTSQTP datasheet(167/404 Pages) MICROCHIP

167 / 404 page

 2004 Microchip Technology Inc.

Preliminary

DS39635A-page 165

PIC18F6310/6410/8310/8410

15.4

PWM Mode

In Pulse-Width Modulation (PWM) mode, the CCP2 pin

produces up to a 10-bit resolution PWM output. Since

the CCP2 pin is multiplexed with a PORTC or PORTE

data latch, the appropriate TRIS bit must be cleared to

make the CCP2 pin an output.

Figure 15-4 shows a simplified block diagram of the

CCP module in PWM mode.

For a step-by-step procedure on how to set up the CCP

module for PWM operation, see Section 15.4.3

“Setup for Pwm Operation”.

FIGURE 15-4:

SIMPLIFIED PWM BLOCK

DIAGRAM

A PWM output (Figure 15-5) has a time base (period)

and a time that the output stays high (duty cycle). The

frequency of the PWM is the inverse of the period

(1/period).

FIGURE 15-5:

PWM OUTPUT

15.4.1

PWM PERIOD

The PWM period is specified by writing to the PR2

following formula:

EQUATION 15-1:

PWM frequency is defined as 1/[PWM period].

When TMR2 is equal to PR2, the following three events

occur on the next increment cycle:

•TMR2 is cleared

• The CCP2 pin is set (exception: if PWM duty

cycle = 0%, the CCP2 pin will not be set)

• The PWM duty cycle is latched from CCPR2L into

CCPR2H

Note:

Clearing the CCP2CON register will force

the RC1 or RE7 output latch (depending

on device configuration) to the default low

level. This is not the PORTC or PORTE

I/O data latch.

CCPR1L

CCPR1H (Slave)

Comparator

TMR2

Comparator

PR2

(Note 1)

Duty Cycle Registers

CCP1CON<5:4>

Clear Timer,

CCP1 pin and

latch D.C.

TRISC<2>

RC2/CCP1

Note 1: The 8-bit TMR2 value is concatenated with the 2-bit

internal Q clock, or 2 bits of the prescaler, to create the

10-bit time base.

Note:

The Timer2 postscalers (see Section 13.0

“Timer2 Module”) are not 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.

Period

Duty Cycle

TMR2 = PR2

TMR2 = Duty Cycle

TMR2 = PR2

PWM Period = (PR2) + 1] • 4 • TOSC •

(TMR2 Prescale Value)

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