DSPIC30F4012 datasheet(105/238 Pages) MICROCHIP

105 / 238 page

DS70135G-page 105

dsPIC30F4011/4012

15.11 PWM Output and Polarity Control

There are three device Configuration bits associated

with the PWM module that provide PWM output pin

control:

• HPOL Configuration bit

• LPOL Configuration bit

• PWMPIN Configuration bit

These three bits in the FBORPOR Configuration regis-

ter (see Section 21.0 “System Integration”) work in

conjunction with the six PWM Enable bits (PENxL and

PENxH). The Configuration bits and PWM Enable bits

ensure that the PWM pins are in the correct states after

a device Reset occurs. The PWMPIN Configuration

fuse allows the PWM module outputs to be optionally

enabled on a device Reset. If PWMPIN = 0, the PWM

outputs will be driven to their inactive states at Reset. If

PWMPIN = 1 (default), the PWM outputs will be tri-

stated. The HPOL bit specifies the polarity for the

PWMxH outputs, whereas the LPOL bit specifies the

polarity for the PWMxL outputs.

15.11.1

OUTPUT PIN CONTROL

The PENxH<3:1> and PENxL<3:1> control bits in the

PWMCON1 SFR enable each high PWM output pin

and each low PWM output pin, respectively. If a

particular PWM output pin is not enabled, it is treated

as a general purpose I/O pin.

15.12 PWM Fault Pin

There is one Fault pin (FLTA) associated with the PWM

module. When asserted, this pin can optionally drive

each of the PWM I/O pins to a defined state.

15.12.1

FAULT PIN ENABLE BITS

The FLTACON SFR has three control bits that deter-

mine whether a particular pair of PWM I/O pins is to be

controlled by the Fault input pin. To enable a

specific PWM I/O pin pair for Fault overrides, the

corresponding bit should be set in the FLTACON

If all enable bits are cleared in the FLTACON register,

then the corresponding Fault input pin has no effect on

the PWM module and the pin may be used as a general

purpose interrupt or I/O pin.

15.12.2

FAULT STATES

The FLTACON Special Function Register has six bits

that determine the state of each PWM I/O pin when it is

overridden by a Fault input. When these bits are

cleared, the PWM I/O pin is driven to the inactive state.

If the bit is set, the PWM I/O pin will be driven to the

active state. The active and inactive states are refer-

enced to the polarity defined for each PWM I/O pin

(HPOL and LPOL polarity control bits).

A special case exists when a PWM module I/O pair is

in the Complementary mode and both pins are

programmed to be active on a Fault condition. The

PWMxH pin always has priority in the Complementary

mode, so that both I/O pins cannot be driven active

simultaneously.

15.12.3

FAULT INPUT MODES

The Fault input pin has two modes of operation:

• Latched Mode: When the Fault pin is driven low,

the PWM outputs will go to the states defined in

the FLTACON register. The PWM outputs will

remain in this state until the Fault pin is driven

high and the corresponding interrupt flag has

been cleared in software. When both of these

actions have occurred, the PWM outputs will

return to normal operation at the beginning of the

next PWM cycle or half-cycle boundary. If the

interrupt flag is cleared before the Fault condition

ends, the PWM module will wait until the Fault pin

is no longer asserted to restore the outputs.

• Cycle-by-Cycle Mode: When the Fault input pin

is driven low, the PWM outputs remain in the

defined Fault states for as long as the Fault pin is

held low. After the Fault pin is driven high, the

PWM outputs return to normal operation at the

beginning of the following PWM cycle or

half-cycle boundary.

The operating mode for the Fault input pin is selected

using the FLTAM control bit in the FLTACON Special

Function Register.

The Fault pin can be controlled manually in software.

Note:

The Fault pin logic can operate indepen-

dent of the PWM logic. If all the enable bits

in the FLTACON register are cleared, then

the Fault pin could be used as a general

purpose interrupt pin. The Fault pin has an

interrupt vector, interrupt flag bit and

interrupt priority bits associated with it.

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