PIC18F6X2X Datasheet, PDF (174/386 Pages) Microchip Technology – 64/80-Pin High Performance, 64-Kbyte Enhanced FLASH Microcontrollers with A/D

PIC18F6X2X/8X2X
17.4.7.1 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 P1RSEN bit of the
ECCP1DEL register (ECCP1DEL<7>).
In Shutdown mode with PRSEN = 1 (Figure 17-10), the
ECCPASE bit will remain set for as long as the cause
of the shutdown continues. When the shutdown condi-
tion clears, the ECCP1ASE bit is cleared. If PRSEN = 0
(Figure 17-11), once a shutdown condition occurs, the
ECCP1ASE bit will remain set until it is cleared by firm-
ware. Once ECCP1ASE is cleared, the enhanced
PWM will resume at the beginning of the next PWM
period.
Note: Writing to the ECCPASE bit is disabled
while a shutdown condition is active.
Independent of the P1RSEN bit setting, if the auto shut-
down source is one of the comparators, the shutdown
condition is a level. The ECCP1ASE 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.
17.4.8 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 polar-
ities must be selected before the PWM pins are config-
ured as 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 applica-
tion 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 com-
pletion of a full PWM cycle is indicated by the TMR2IF
bit being set as the second PWM period begins.
FIGURE 17-10: PWM AUTO SHUTDOWN (PRSEN = 1, AUTO RESTART ENABLED)
Shutdown Event
PWM Period
ECCPASE bit
PWM Activity
Start of
PWM Period
Normal PWM
Shutdown Shutdown
Event Occurs Event Clears
PWM
Resumes
FIGURE 17-11: PWM AUTO SHUTDOWN (PRSEN = 0, AUTO RESTART DISABLED)
Shutdown Event
PWM Period
ECCPASE bit
PWM Activity
Start of
PWM Period
Normal PWM
Shutdown
Event Occurs
ECCPASE
Cleared by
Shutdown Firmware PWM
Event Clears
Resumes
DS39612A-page 172
Advance Information
 2003 Microchip Technology Inc.