mc9s12e256 Freescale Semiconductor, Inc, mc9s12e256 Datasheet - Page 353

• Manufacturer Part Number: mc9s12e256
• Description: Hcs12 Microcontrollers 16-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

11.4
11.4.1
A block diagram of the PMF is shown in
generators (A, B, and C) or just a single generator (A). PWM0 and PWM1 constitute Pair A, PWM2 and
PWM3 constitute Pair B, and PWM4 and PWM5 constitute Pair C.
11.4.2
To permit lower PWM frequencies, the prescaler produces the PWM clock frequency by dividing the bus
clock frequency by one, two, four, and eight. Each PWM generator has its own prescaler divisor. Each
prescaler is buffered and will not be used by its PWM generator until the corresponding Load OK bit is set
and a new PWM reload cycle begins.
11.4.3
Each PWM generator contains a 15-bit up/down PWM counter producing output signals with
software-selectables:
11.4.3.1
Each edge-align bit, EDGEx, selects either center-aligned or edge-aligned PWM generator outputs.
Freescale Semiconductor
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Alignment—The logic state of each pair EDGE bit determines whether the PWM pair outputs are
edge-aligned or center-aligned
Period—The value written to each pair PWM counter modulo register is used to determine the
PWM pair period. The period can also be varied by using the prescaler
— With edge-aligned output, the modulus is the period of the PWM output in clock cycles
— With center-aligned output, the modulus is one-half of the PWM output period in clock cycles
Pulse width—The number written to the PWM value register determines the pulse width duty cycle
of the PWM output in clock cycles
— With center-aligned output, the pulse width is twice the value written to the PWM value register
— With edge-aligned output, the pulse width is the value written to the PWM value register
Functional Description
Block Diagram
Prescaler
PWM Generator
Alignment
ALIGNMENT REFERENCE
UP/DOWN COUNTER
DUTY CYCLE = 50%
PWM OUTPUT
MODULUS = 4
Figure 11-41. Center-Aligned PWM Output
MC9S12E256 Data Sheet, Rev. 1.08
Figure
11-1. The MTG bit allows the use of multiple PWM
Chapter 11 Pulse Width Modulator with Fault Protection (PMF15B6CV2)
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