PIC16LC717T-I/SO View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC16LC717T-I/SO

18/20-Pin, 8-Bit CMOS Microcontrollers with 10/12-Bit A/D

Microchip Technology 

PIC16C717/770/771

8.3 PWM Mode

In Pulse Width Modulation (PWM) mode, the ECCP

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

Figure 8-3 shows the simplified PWM block diagram.

FIGURE 8-3:

SIMPLIFIED PWM BLOCK DIAGRAM

Duty cycle registers

CCPR1L

CCP1CON<5:4>

CCPR1H (Slave)

Comparator

R

Q

TMR2

(Note 1)

S

Comparator

PR2

Clear Timer,

CCP1 pin and

latch D.C.

PWM1M1<1:0> CCP1M<3:0>

2

4

CCP1/P1A

P1B

OUTPUT

CONTROLLER

P1C

P1D

P1DEL

TRISB<3>

TRISB<5>

TRISB<6>

TRISB<7>

RB3/CCP1/P1A

RB5/SDO/P1B

RB6/T1OSO/T1CKI/

P1C

RB7/T1OSI/P1D

Note: 8-bit timer TMR2 is concatenated with 2-bit internal Q clock or 2 bits of the prescaler to create 10-bit time-base.

8.3.1 PWM PERIOD

The PWM period is specified by writing to the PR2 reg-

ister. The PWM period can be calculated using the fol-

lowing formula:

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 7.0) is

not used in the determination of the PWM

frequency. The postscaler could be used to

have a servo update rate at a different fre-

quency than the PWM output.

DS41120A-page 58

Advanced Information

© 1999 Microchip Technology Inc.

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