DSPIC33FJ06GS202 datasheet(13/20 Pages) MICROCHIP

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DS80439M-page 13

dsPIC33FJ06GS101/X02 and dsPIC33FJ16GSX02/X04

32. Module: High-Speed PWM

The PENH and PENL bits in the IOCONx register

are used to assign ownership of the pins to either

the PWM module or the GPIO module. The correct

procedure to configure the PWM module is to

assign pin ownership to the PWM module and then

enabling it using the PTEN bit in the PTCON

If the PWM module is enabled using the above

sequence, then a glitch may be observed on the

PWM pins before actual switching of the PWM

outputs begins. This glitch may cause momentary

turn-on of power MOSFETs that are driven by the

PWM pins and may cause damage to the

application hardware.

Work around

Follow the given sequence to avoid any glitches

from appearing on the PWM outputs at the time of

enabling.

1. Configure the respective PWM pins to digital

inputs using the TRISx registers. This step will

put the PWM pins in a high-impedance state.

The PWM outputs must be maintained in a safe

state by using pull-up or pull-down resistors.

2. Assign pin ownership to the GPIO module by

configuring IOCONx<PENH> = 0

and

IOCONx<PENL> = 0.

3. Specify the PWM override state to the desired

safe state for the PWM pins using the

OVRDAT<1:0> bit field in the IOCONx register.

4. Override

the

PWM

outputs

setting

IOCONx<OVRENH> = 1

and

IOCONx<OVRENL> = 1.

5. Enable

the

PWM

module

setting

PTCON<PTEN> = 1.

6. Remove

the

PWM

overrides

making IOCONx<OVRENH> = 0 and

IOCONx<OVRENL> = 0.

7. Ensure a delay of at least one full PWM cycle.

8. Assign pin ownership to the PWM module

by setting IOCONx<PENH> = 1 and

IOCONx<PENL> = 1.

The code in Example 3 illustrates the use of this

work around.

Affected Silicon Revisions

EXAMPLE 3:

CONFIGURE PWM MODULE TO PREVENT GLITCHES ON PWM1H AND PWM1L

PINS AT THE TIME OF ENABLING

TRISAbits.TRISA4 = 1;

// Configure PWM1H/RA4 as digital input

// Ensure output is in safe state using pull-up or

// pull-down resistors

TRISAbits.TRISA3 = 1;

// Configure PWM1L/RA3 as digital input

// Ensure output is in safe state using pull-up or

// pull-down resistors

IOCON1bits.PENH = 0;

// Assign pin ownership of PWM1H/RA4 to GPIO module

IOCON1bits.PENL = 0;

// Assign pin ownership of PWM1L/RA3 to GPIO module

IOCON1bits.OVRDAT = 0;

// Configure override state of the PWM outputs to

// desired safe state.

IOCON1bits.OVRENH = 1;

// Override PWM1H output

IOCON1bits.OVRENL = 1;

// Override PWM1L output

PTCONbits.PTEN = 1;

// Enable PWM module

IOCON1bits.OVRENH = 0;

// Remove override for PWM1H output

IOCON1bits.OVRENL = 0;

// Remove override for PWM1L output

Delay(x);

// Introduce a delay greater than one full PWM cycle

IOCON1bits.PENH = 1;

// Assign pin ownership of PWM1H/RA4 to PWM module

IOCON1bits.PENL = 1;

// Assign pin ownership of PWM1L/RA3 to PWM module

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