Datasheet
PIC16(L)F1782/3
DS41579D-page 230 Preliminary 2011-2012 Microchip Technology Inc.
24.6 PSMC Modulation (Burst Mode)
PSMC modulation is a method to stop/start PWM
operation of the PSMC without having to disable the
module. It also allows other modules to control the
operational period of the PSMC. This is also referred
to as Burst mode.
This is a method to implement PWM dimming.
24.6.1 MODULATION ENABLE
The modulation function is enabled by setting the
PxMDLEN bit of PSMC Modulation Control
(PSMCxMDL) register (Register 24-2).
When modulation is enabled, the modulation source
controls when the PWM signals are active and
inactive.
When modulation is disabled, the PWM signals
operate continuously, regardless of the selected
modulation source.
24.6.2 MODULATION SOURCES
There are multiple sources that can be used for
modulating the PSMC. However, unlike the PSMC
input sources, only one modulation source can be
selected at a time. Modulation sources include:
• PSMCxIN pin
• Any CCP output
• Any Comparator output
• PxMDLBIT of the PSMCxMDL register
24.6.2.1 PxMDLBIT Bit
The PxMDLBIT bit of the PSMC Modulation Control
(PSMCxMDL) register (Register 24-2) allows for
software modulation control without having to
enable/disable other module functions.
24.6.3 MODULATION EFFECT ON PWM
SIGNALS
When modulation starts, the PSMC begins operation
on a new period, just as if it had rolled over from one
period to another during continuous operation.
When modulation stops, its operation depends on the
type of waveform being generated.
In operation modes other than Fixed Duty Cycle, the
PSMC completes its current PWM period and then
freezes the module. The PSMC output pins are forced
into the default inactive state ready for use when
modulation starts.
In Fixed Duty Cycle mode operation, the PSMC
continues to operate until the period event changes
the PWM to its inactive state, at which point the PSMC
module is frozen. The PSMC output pins are forced
into the default inactive state ready for use when
modulation starts.
FIGURE 24-19: PSMC MODULATION WAVEFORM
1 2 3 4 5 6 7 1 1 2 3 4 5
PWM PWM PWM OffPWM OffPWM OffPWM Off
Modulation Input
PWM Period
Off