Datasheet

PIC16(L)F1782/3
DS41579D-page 206 Preliminary  2011-2012 Microchip Technology Inc.
24.1.1 PERIOD EVENT
The period event determines the frequency of the
active pulse. Period event sources include any
combination of the following:
• PSMCxTMR counter match
• PSMC input pin
• sync_C1OUT
• sync_C2OUT
• sync_C3OUT
Period event sources are selected with the PSMC
Period Source (PSMCxPRS) register (Register 24-13).
Section 24.2.1.2 “16-bit Period Register” contains
details on configuring the PSMCxTMR counter match
for synchronous period events.
All period events cause the PSMCxTMR counter to
reset on the counting clock edge immediately following
the period event. The PSMCxTMR counter resumes
counting from zero on the counting clock edge after the
period event Reset.
During a period, the rising event and falling event are
each permitted to occur only once. Subsequent rising
or falling events that may occur within the period are
suppressed, thereby preventing output chatter from
spurious inputs.
24.1.2 RISING EDGE EVENT
The rising edge event determines the start of the active
drive period. The rising edge event is also referred to
as the phase because two synchronized PSMC periph-
erals may have different rising edge events relative to
the period start, thereby creating a phase relationship
between the two PSMC peripheral outputs.
Depending on the PSMC mode, one or more of the
PSMC outputs will change in immediate response to
the rising edge event. Rising edge event sources
include any combination of the following:
• Synchronous:
- PSMCxTMR time base counter match
• Asynchronous:
- PSMC input pin
- sync_C1OUT
- sync_C2OUT
- sync_C3OUT
Rising edge event sources are selected with the PSMC
Phase Source (PSMCxPHS) register (Register 24-11).
For configuring the PSMCxTMR time base counter
match for synchronous rising edge events, see
Section 24.2.1.3 “16-bit Phase Register”.
The first rising edge event in a cycle period is the only
one permitted to cause action. All subsequent rising
edge events in the same period are suppressed to
prevent the PSMC output from chattering in the
presence of spurious event inputs. A rising edge event
is also suppressed when it occurs after a falling edge
event in the same period.
The rising edge event also triggers the start of two
other timers when needed: falling edge blanking and
dead-band period. For more detail refer to
Section 24.2.8 “Input Blanking” and Section 24.4
“Dead-Band Control”
.
When the rising edge event is delayed from the period
start, the amount of delay subtracts from the total
amount of time available for the drive duty cycle. For
example, if the rising edge event is delayed by 10% of
the period time, the maximum duty cycle for that period
is 90%. A 100% duty cycle is still possible in this
example, but duty cycles from 90% to 100% are not
possible.
24.1.3 FALLING EDGE EVENT
The falling edge event determines the end of the active
drive period. The falling edge event is also referred to
as the duty cycle because varying the falling edge
event, while keeping the rising edge event and period
events fixed, varies the active drive duty cycle.
Depending on the PSMC mode, one or more of the
PSMC outputs will change in immediate response to
the falling edge event. Falling edge event sources
include any combination of the following:
• Synchronous:
- PSMCxTMR time base counter match
• Asynchronous:
- PSMC input pin
- sync_C1OUT
- sync_C2OUT
- sync_C3OUT
Falling edge event sources are selected with PSMC Duty
Cycle Source (PSMCxDCS) register (Register 24-12).
For configuring the PSMCxTMR time base counter
match for synchronous falling edge events, see
Section 24.2.1.4 “16-bit Duty Cycle Register”.
The first falling edge event in a cycle period is the only
one permitted to cause action. All subsequent falling
edge events in the same period are suppressed to
prevent the PSMC output from chattering in the
presence of spurious event inputs.
A falling edge event suppresses any subsequent rising
edges that may occur in the same period. In other
words, if an asynchronous falling event input should
come late and occur early in the period, following that
for which it was intended, the rising edge in that period
will be suppressed. This will have a similar effect as
pulse skipping.
The falling edge event also triggers the start of two
other timers: rising edge blanking and dead-band
period. For more detail refer to
Section 24.2.8 “Input
Blanking”
and Section 24.4 “Dead-Band Control”.