PIC18F4685-ISLASHSP datasheet(187/484 Pages) MICROCHIP

187 / 484 page

Preliminary

DS39761B-page 185

PIC18F2682/2685/4682/4685

16.4.9

SETUP FOR PWM OPERATION

The following steps should be taken when configuring

the ECCP1 module for PWM operation:

Configure the PWM pins, P1A and P1B (and

P1C and P1D, if used), as inputs by setting the

corresponding TRIS bits.

Set the PWM period by loading the PR2 register.

Configure the ECCP1 module for the desired

PWM mode and configuration by loading the

ECCP1CON register with the appropriate values:

• Select one of the available output

configurations and direction with the

EPWM1M1:EPWM1M0 bits.

• Select the polarities of the PWM output

signals with the ECCP1M3:ECCP1M0 bits.

Set the PWM duty cycle by loading the

ECCPR1L register and ECCP1CON<5:4> bits.

For Half-Bridge Output mode, set the dead-

band delay by loading ECCP1DEL<6:0> with

the appropriate value.

If auto-shutdown operation is required, load the

ECCP1AS register:

• Select the auto-shutdown sources using the

ECCPAS2:ECCPAS0 bits.

• Select the shutdown states of the PWM

output pins using PSSAC1:PSSAC0 and

PSSBD1:PSSBD0 bits.

• Set the ECCPASE bit (ECCP1AS<7>).

• Configure the comparators using the CMCON

• Configure the comparator inputs as analog

inputs.

If auto-restart operation is required, set the

PRSEN bit (ECCP1DEL<7>).

Configure and start TMR2:

• Clear the TMR2 interrupt flag bit by clearing

the TMR2IF bit (PIR1<1>).

• Set the TMR2 prescale value by loading the

T2CKPS bits (T2CON<1:0>).

• Enable Timer2 by setting the TMR2ON bit

(T2CON<2>).

Enable PWM outputs after a new PWM cycle

has started:

• Wait until TMRx overflows (TMRxIF bit is set).

• Enable the ECCP1/P1A, P1B, P1C and/or

P1D pin outputs by clearing the respective

TRIS bits.

• Clear the ECCPASE bit (ECCP1AS<7>).

16.4.10

EFFECTS OF A RESET

Both Power-on Reset and subsequent Resets will force

all ports to Input mode and the ECCP1 registers to their

Reset states.

This forces the Enhanced CCP1 module to reset to a

state compatible with the standard CCP1 module.

PIC18F4685-I/SP Datasheet(PDF) 187 Page - Microchip Technology

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