PIC12F1822 MICROCHIP [Microchip Technology], PIC12F1822 Datasheet - Page 215

• Manufacturer Part Number: PIC12F1822
• Description: 8/14-Pin Flash Microcontrollers with nanoWatt XLP Technology
• Manufacturer: MICROCHIP [Microchip Technology]

FIGURE 23-13:
23.4.3
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
CCP1AS<2:0> bits of the CCP1AS register. A shutdown
event may be generated by:
• A logic ‘0’ on the INT pin
• Comparator C1
• Setting the CCP1ASE bit in firmware
A shutdown condition is indicated by the CCP1ASE
(Auto-Shutdown Event Status) bit of the CCP1AS
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 CCP1ASE bit is set to ‘1’. The CCP1ASE will
remain set until cleared in firmware or an auto-restart
occurs (see Section 23.4.4 “Auto-Restart Mode”).
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
 2010 Microchip Technology Inc.
Shoot-Through Current
Note 1: All signals are shown as active-high.
External Switch C
External Switch D
2: T
3: T
ENHANCED PWM AUTO-
SHUTDOWN MODE
ON
OFF
Potential
is the turn-on delay of power switch QC and its driver.
is the turn-off delay of power switch QD and its driver.
P1A
P1B
P1C
P1D
EXAMPLE OF PWM DIRECTION CHANGE AT NEAR 100% DUTY CYCLE
Forward Period
PIC12F/LF1822/16F/LF1823
PW
Preliminary
of each pin pair is determined by the PSS1AC and
PSS1BD bits of the CCP1AS register. Each pin pair may
be placed into one of three states:
• Drive logic ‘1’
• Drive logic ‘0’
• Tri-state (high-impedance)
Note 1: The auto-shutdown condition is a level-
t1
2: Writing to the CCP1ASE bit is disabled
3: Once the auto-shutdown condition has
based signal, not an edge-based signal.
As long as the level is present, the auto-
shutdown will persist.
while
persists.
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.
T
ON
Reverse Period
T
T = T
OFF
an
OFF
PW
– T
auto-shutdown
ON
DS41413A-page 215
condition