PXS20RM Datasheet, PDF (651/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Flexible Motor Control Pulse Width Modulator Module (FlexPWM)
25.2.4 EXT_SYNC - External Synchronization Signal
This input signal allows a source external to the PWM to initialize the PWM counter. In this manner the
PWM can be synchronized to external circuitry.
25.2.5 EXT_FORCE - External Output Force Signal
This input signal allows a source external to the PWM to force an update of the PWM outputs. In this
manner the PWM can be synchronized to external circuitry. An example would be to simultaneously
switch all of the PWM outputs on a commutation boundary for trapezoidal control of a BLDC motor. The
boundary can be established via external logic or an on-chip timer.
25.2.6 EXTA[n] and EXTB[n] - Alternate PWM Control Signals
These pins allow an alternate source to control the PWMA and PWMB outputs although typically, the
EXTA input will be used for the generation of a complementary pair. Typical connections include ADC
results registers, TMR outputs, GPIO inputs, and comparator outputs. The SIM chapter of the chip system
spec will describe the possible connections and the bits to control any muxing.
25.2.7 OUT_TRIG0[n] and OUT_TRIG1[n] - Output Triggers
These outputs allow the PWM submodules to control timing of the ADC conversions. See 25.4.3.15,
Output Trigger Control Register (TCTRL) for a description of how to enable these outputs and how the
compare registers match up to the output triggers.
25.2.8 EXT_CLK - External Clock Signal
This on-chip input signal allows an on-chip source external to the PWM (typically a Timer) to control the
PWM clocking. In this manner the PWM can be synchronized to the Timer. This signal must be generated
synchronously to the PWM’s clock since it is not resynchronized in the PWM.
25.3 Functional Description
25.3.1 Block Diagram
A block diagram of the PWM is shown in Figure 25-1.
25.3.2 PWM Capabilities
This section describes some capabilities of the PWM module.
25.3.2.1 Center Aligned PWMs
Each submodule has its own timer that is capable of generating PWM signals on two output pins. The
edges of each of these signals are controlled independently as shown in Figure 25-3.
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
25-5