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PIC16LF1946_13 Datasheet, PDF (232/478 Pages) Microchip Technology – 64-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver and nanoWatt XLP Technology | |||
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PIC16(L)F1946/47
23.4.3 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 â0â on the INT pin
⢠A logic â0â on a Comparator (async_CxOUT) output
A shutdown condition is indicated by the CCPxASE
(Auto-Shutdown Event Status) bit of the CCPxAS
register. If the bit is a â0â, the PWM pins are operating
normally. If the bit is a â1â, the PWM outputs are in the
shutdown state.
When a shutdown event occurs, two things happen:
The CCPxASE bit is set to â1â. The CCPxASE will
remain set until cleared in firmware or an auto-restart
occurs (see Section 23.4.4 âAuto-Restart Modeâ).
The enabled PWM pins are asynchronously placed in
their shutdown states. The PWM output pins are
grouped into pairs [PxA/PxC] and [PxB/PxD]. 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 â1â
⢠Drive logic â0â
⢠Tri-state (high-impedance)
Note 1: The auto-shutdown condition is a
level-based signal, not an edge-based
signal. As long as the level is present, the
auto-shutdown will persist.
2: Writing to the CCPxASE bit of the
CCPxAS register is disabled while an
auto-shutdown condition persists.
3: Once the auto-shutdown condition has
been removed and the PWM restarted
(either through firmware or auto-restart)
the PWM signal will always restart at the
beginning of the next PWM period.
4: Prior to an auto-shutdown event caused
by a comparator output or INT pin event,
a software shutdown can be triggered in
firmware by setting the CCPxASE bit of
the CCPxAS register to â1â. The
Auto-Restart feature tracks the active
status of a shutdown caused by a
comparator output or INT pin event only.
If it is enabled at this time, it will
immediately clear this bit and restart the
ECCP module at the beginning of the
next PWM period.
DS41414D-page 232
ï£ 2010-2012 Microchip Technology Inc.
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