Microchip Technology AC244045 Data Sheet
PIC16(L)F1825/1829
DS41440C-page 234
2010-2012 Microchip Technology Inc.
24.4.6.1
Steering Synchronization
The STRxSYNC bit of the PSTRxCON register gives
the user two selections of when the steering event will
happen. When the STRxSYNC bit is ‘0’, the steering
event will happen at the end of the instruction that
writes to the PSTRxCON register. In this case, the
output signal at the Px<D:A> pins may be an
incomplete PWM waveform. This operation is useful
when the user firmware needs to immediately remove
a PWM signal from the pin.
When the STRxSYNC bit is ‘1’, the effective steering
update will happen at the beginning of the next PWM
period. In this case, steering on/off the PWM output will
always produce a complete PWM waveform.
Figures
the user two selections of when the steering event will
happen. When the STRxSYNC bit is ‘0’, the steering
event will happen at the end of the instruction that
writes to the PSTRxCON register. In this case, the
output signal at the Px<D:A> pins may be an
incomplete PWM waveform. This operation is useful
when the user firmware needs to immediately remove
a PWM signal from the pin.
When the STRxSYNC bit is ‘1’, the effective steering
update will happen at the beginning of the next PWM
period. In this case, steering on/off the PWM output will
always produce a complete PWM waveform.
Figures
and
illustrate the timing diagrams
of the PWM steering depending on the STRxSYNC
setting.
setting.
24.4.7
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.
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 (PxA/PxC and PxB/PxD). The PWM output
polarities must be selected before the PWM pin output
drivers are enabled. Changing the polarity
hardware must use the proper external pull-up and/or
pull-down resistors on the PWM output pins.
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 (PxA/PxC and PxB/PxD). 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 PxA, PxB, PxC and PxD 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.
enable is not recommended since it may result in
damage to the application circuits.
The PxA, PxB, PxC and PxD 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.
24.4.8
ALTERNATE PIN LOCATIONS
This module incorporates I/O pins that can be moved to
other locations with the use of the alternate pin function
registers, APFCON0 or APFCON1. To determine
which pins can be moved and what their default
locations are upon a Reset, see
other locations with the use of the alternate pin function
registers, APFCON0 or APFCON1. To determine
which pins can be moved and what their default
locations are upon a Reset, see
for more information.
FIGURE 24-19:
EXAMPLE OF STEERING EVENT AT END OF INSTRUCTION (STRxSYNC = 0)
FIGURE 24-20:
EXAMPLE OF STEERING EVENT AT BEGINNING OF INSTRUCTION
(STRxSYNC = 1)
(STRxSYNC = 1)
Note:
When the microcontroller is released from
Reset, all of the I/O pins are in the high-
impedance state. The external circuits
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).
Reset, all of the I/O pins are in the high-
impedance state. The external circuits
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).
PWM
P1n = PWM
STRx
P1<D:A>
PORT Data
PWM Period
PORT Data
PWM
PORT Data
P1n = PWM
STRx
P1<D:A>
PORT Data