PIC16F716 datasheet(49/126 Pages) MICROCHIP

49 / 126 page

 2003 Microchip Technology Inc.

Preliminary

DS41206A-page 47

PIC16F716

7.4.5.1

Auto-Shutdown and Automatic

Restart

The auto-shutdown feature can be configured to allow

automatic restarts of the module following a shutdown

event. This is enabled by setting the PRSEN bit of the

PWM1CON register (PWM1CON<7>).

In Shutdown mode with PRSEN = 1 (PWM1CON <7>)

(Figure 7-15), the ECCPASE bit will remain set for as

long as the cause of the shutdown continues. When the

shutdown condition clears, the ECCPASE bit is

cleared. If PRSEN = 0 (Figure 7-16), once a shutdown

condition occurs, the ECCPASE bit will remain set until

it is cleared by firmware. Once ECCPASE is cleared,

the enhanced PWM will resume at the beginning of the

next PWM period.

The ECCPASE bit cannot be cleared as long as the

cause of the shutdown persists.

The Auto-shutdown mode can be forced by writing a '1'

to the ECCPASE bit.

7.4.6

START-UP CONSIDERATIONS

When the ECCP module is used in the PWM mode, the

application hardware must use the proper external pull-

up and/or pull-down resistors on the PWM output pins.

When the microcontroller is released from Reset, all of

the I/O pins are in the high-impedance state. The

external circuits must keep the power switch devices in

the off state, until the microcontroller drives the I/O pins

with the proper signal levels, or activates the PWM

output(s).

The CCP1M1:CCP1M0 bits (CCP1CON<1:0>) allow

the user to choose whether the PWM output signals are

active-high or active-low for each pair of PWM output

pins (P1A/P1C and P1B/P1D). The PWM output

polarities must be selected before the PWM pins are

configured

outputs.

Changing

the

polarity

configuration while the PWM pins are configured as

outputs is not recommended since it may result in

damage to the application circuits.

The P1A, P1B, P1C and P1D output latches may not

be in the proper states when the PWM module is

initialized. Enabling the PWM pins for output at the

same time as the ECCP module may cause damage to

the application circuit. The ECCP module must be

enabled in the proper Output mode and complete a full

PWM cycle before configuring the PWM pins as

outputs. The completion of a full PWM cycle is

indicated by the TMR2IF bit being set as the second

PWM period begins.

FIGURE 7-15:

PWM AUTO-SHUTDOWN (PRSEN = 1, AUTO-RESTART ENABLED)

FIGURE 7-16:

PWM AUTO-SHUTDOWN (PRSEN = 0, AUTO-RESTART DISABLED)

Note:

Writing to the ECCPASE bit is disabled

while a shutdown condition is active.

Shutdown

PWM

ECCPASE bit

Activity

Event

Shutdown

Event Occurs

Shutdown

Event Clears

PWM

Resumes

Normal PWM

Start of

PWM Period

Shutdown

PWM

ECCPASE bit

Activity

Event

Shutdown

Event Occurs

Shutdown

Event Clears

PWM

Resumes

Normal PWM

Start of

PWM Period

ECCPASE

Cleared by

Firmware

PWM Period

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