PIC18F45J10 Datasheet, PDF (144/358 Pages) Microchip Technology – 28/40/44-Pin High-Performance RISC Microcontrollers with nanoWatt Technology

PIC18F45J10 FAMILY
14.4.7.1 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 PRSEN bit of the
ECCP1DEL register (ECCP1DEL<7>).
In Shutdown mode with PRSEN = 1 (Figure 14-10), the
ECCPASE bit will remain set for as long as the cause
of the shutdown continues. When the shutdown condi-
tion clears, the ECCPASE bit is cleared. If PRSEN = 0
(Figure 14-11), once a shutdown condition occurs, the
ECCPASE bit will remain set until it is cleared by firm-
ware. Once ECCPASE 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 PRSEN bit setting, if the auto-
shutdown source is one of the comparators, the
shutdown condition is a level. 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.
14.4.8 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
polarities must be selected before the PWM pins are
configured as outputs. Changing the polarity configura-
tion 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 14-10: 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 14-11: 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
DS39682C-page 142
Preliminary
© 2007 Microchip Technology Inc.