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Chapter 14 Pulse Width Modulator with Fault Protection (PMF15B6CV3)
MC9S12ZVM Family Reference Manual Rev. 1.3
486
Freescale Semiconductor
14.1
Introduction
The Pulse width Modulator with Fault protection (PMF) module can be configured for one, two, or three
complementary pairs. For example:
•
One complementary pair and four independent PWM outputs
•
Two complementary pairs and two independent PWM outputs
•
Three complementary pairs and zero independent PWM outputs
•
Zero complementary pairs and six independent PWM outputs
All PWM outputs can be generated from the same counter, or each pair can have its own counter for three
independent PWM frequencies. Complementary operation permits programmable deadtime insertion,
distortion correction through current sensing by software, and separate top and bottom output polarity
control. Each counter value is programmable to support a continuously variable PWM frequency. Both
edge- and center-aligned synchronous pulse width-control and full range modulation from 0 percent to 100
percent, are supported. The PMF is capable of controlling most motor types: AC induction motors
(ACIM), both brushless (BLDC) and brush DC motors (BDC), switched (SRM) and variable reluctance
motors (VRM), and stepper motors.
14.1.1
Features
•
Three complementary PWM signal pairs, or six independent PWM signals
•
Edge-aligned or center-aligned mode
•
Features of complementary channel operation:
— Deadtime insertion
— Separate top and bottom pulse width correction via current status inputs or software
— Three variants of PWM output:
PWM cycle
PWM period determined by modulus register and PWM clock rate. Note the differences in edge- or center-
aligned mode.
PWM reload cycle
A.k.a. control cycle. Determined by load frequency which is 1 to n-times the PWM cycle. PWM reload cycle
triggered double-buffered registers take effect at the next PWM reload event.
Commutation cycle For 6-step motor control only. Started by an event external to the PMF module (async_event). This may be
a delayed Hall effect or back-EMF zero crossing event determining the rotor position. Commutation cycle
triggered double-buffered registers take effect at the next commutation event and optionally the PWM
counters are restarted.
Index x
Related to time bases. x = A, B or C
Index n
Related to PWM channels. n = 0, 1, 2, 3, 4, or 5
Index m
Related to fault inputs. m = 0, 1, 2, 3, 4, or 5
Table 14-2. Glossary of Terms
Term
Definition