PIC16F193X Datasheet, PDF (205/418 Pages) Microchip Technology – 28/40/44-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver and nanoWatt Technology

19.6.3 START-UP CONSIDERATIONS
When any PWM mode is used, the application
hardware must use the proper external pull-up and/or
pull-down resistors on the PWM output pins.
Note:
When the microcontroller is released from
Reset, all of the I/O pins are in the
high-impedance state. The external cir-
cuits 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 CCPxM<1:0> bits of the CCPxCON register 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 pin output drivers are
enabled. Changing the polarity configuration while the
PWM pin output drivers are enable 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 pin output drivers at the
same time as the Enhanced PWM modes may cause
damage to the application circuit. The Enhanced PWM
modes must be enabled in the proper Output mode and
complete a full PWM cycle before enabling the PWM
pin output drivers. The completion of a full PWM cycle
is indicated by the TMRxIF bit of the PIRx register
being set as the second PWM period begins.
19.6.4 ENHANCED PWM
AUTO-SHUTDOWN MODE
The PWM mode supports an Auto-Shutdown mode that
will disable the PWM outputs when an external
shutdown event occurs. Auto-Shutdown mode places
the PWM output pins into a predetermined state. This
mode is used to help prevent the PWM from damaging
the application.
The auto-shutdown sources are selected using the
CCPxAS<2:0> bits of the CCPxAS register. A shutdown
event may be generated by:
• A logic ‘0’ on the INT pin
• Comparator Cx
• Setting the CCPxASE bit in firmware
A shutdown condition is indicated by the CCPxASE
(Auto-Shutdown Event Status) bit of the CCPxAS
register. If the bit is a ‘0’, the PWM pins are operating
normally. If the bit is a ‘1’, the PWM outputs are in the
shutdown state.
When a shutdown event occurs, two things happen:
The CCPxASE bit is set to ‘1’. The CCPxASE will
remain set until cleared in firmware or an auto-restart
occurs (see Section 19.6.5 “Auto-Restart Mode”).
PIC16F193X/LF193X
The enabled PWM pins are asynchronously placed in
their shutdown states. The PWM output pins are
grouped into pairs [P1A/P1C] and [P1B/P1D]. The state
of each pin pair is determined by the PSSxAC and
PSSxBD bits of the CCPxAS register. Each pin pair may
be placed into one of three states:
• Drive logic ‘1’
• Drive logic ‘0’
• Tri-state (high-impedance)
© 2008 Microchip Technology Inc.
Preliminary
DS41364A-page 203