PIC16F716-I/P View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC16F716-I/P

8-bit Flash-based Microcontroller with A/D Converter and Enhanced Capture/Compare/PWM

Microchip Technology 

PIC16F716

7.3 PWM Mode

In Pulse Width Modulation (PWM) mode, the CCP1 pin

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

the CCP1 pin is multiplexed with the PORTB data latch,

the TRISB<3> bit must be cleared to make the CCP1

pin an output.

Note:

Clearing the CCP1CON register will force

the CCP1 PWM output latch to the default

low level. This is not the PORTB I/O data

latch.

Figure 7-3 shows a simplified block diagram of the

CCP module in PWM mode.

For a step-by-step procedure on how to setup the

ECCP module for PWM operation, see Section 7.3.3

“Set-Up for PWM Operation”.

FIGURE 7-3:

SIMPLIFIED PWM BLOCK

DIAGRAM

Duty cycle registers

CCPR1L

CCP1CON<5:4>

CCPR1H (Slave)

Comparator

RB3/CCP1/P1A

R

Q

TMR2

(Note 1)

S

Comparator

PR2

Clear Timer,

CCP1 pin and

latch D.C.

TRISB<3>

Note 1: 8-bit timer is concatenated with 2-bit internal Q clock

or 2 bits of the prescaler to create 10-bit time base.

A PWM output (Figure 7-4) 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 7-4:

PWM OUTPUT

Period = PR2+1

Duty Cycle

TMR2 = PR2

TMR2 = Duty Cycle (CCPR1H)

TMR2 = PR2

7.3.1 PWM PERIOD

The PWM period is specified by writing to the PR2

register. The PWM period can be calculated using the

following formula:

EQUATION 7-1:

PWM Period = [(PR2) + 1] • 4 • Tosc •

(TMR2 prescale value)

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 CCP1 pin is set (exception: if PWM duty

cycle = 0%, the CCP1 pin will not be set)

• The PWM duty cycle is latched from CCPR1L into

CCPR1H

Note:

The Timer2 postscaler (see Section 6.0

“Timer2 Module”) is 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.

DS41206A-page 36

Preliminary

 2003 Microchip Technology Inc.

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