PIC12F1822T-I/SL 查看數據表（PDF） - Microchip Technology
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PIC12F1822T-I/SL Datasheet PDF : 398 Pages
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PIC12F/LF1822/16F/LF1823
FIGURE 23-13:
EXAMPLE OF PWM DIRECTION CHANGE AT NEAR 100% DUTY CYCLE
Forward Period
t1
Reverse Period
P1A
P1B
P1C
P1D
PW
External Switch C
External Switch D
Potential
Shoot-Through Current
PW
TON
TOFF
T = TOFF – TON
Note 1: All signals are shown as active-high.
2: TON is the turn-on delay of power switch QC and its driver.
3: TOFF is the turn-off delay of power switch QD and its driver.
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
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
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-
based signal, not an edge-based signal.
As long as the level is present, the auto-
shutdown will persist.
2: Writing to the CCP1ASE bit 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.
2010 Microchip Technology Inc.
Preliminary
DS41413A-page 215
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