MC9S12XD256MAL Datasheet, PDF (363/1348 Pages) Freescale Semiconductor, Inc – Freescale’s Scalable Controller Area Network

Chapter 8
Pulse-Width Modulator (S12PWM8B8CV1)
8.1 Introduction
The PWM definition is based on the HC12 PWM definitions. It contains the basic features from the HC11
with some of the enhancements incorporated on the HC12: center aligned output mode and four available
clock sources.The PWM module has eight channels with independent control of left and center aligned
outputs on each channel.
Each of the eight channels has a programmable period and duty cycle as well as a dedicated counter. A
flexible clock select scheme allows a total of four different clock sources to be used with the counters. Each
of the modulators can create independent continuous waveforms with software-selectable duty rates from
0% to 100%. The PWM outputs can be programmed as left aligned outputs or center aligned outputs.
8.1.1 Features
The PWM block includes these distinctive features:
• Eight independent PWM channels with programmable period and duty cycle
• Dedicated counter for each PWM channel
• Programmable PWM enable/disable for each channel
• Software selection of PWM duty pulse polarity for each channel
• Period and duty cycle are double buffered. Change takes effect when the end of the effective period
is reached (PWM counter reaches zero) or when the channel is disabled.
• Programmable center or left aligned outputs on individual channels
• Eight 8-bit channel or four 16-bit channel PWM resolution
• Four clock sources (A, B, SA, and SB) provide for a wide range of frequencies
• Programmable clock select logic
• Emergency shutdown
8.1.2 Modes of Operation
There is a software programmable option for low power consumption in wait mode that disables the input
clock to the prescaler.
In freeze mode there is a software programmable option to disable the input clock to the prescaler. This is
useful for emulation.
MC9S12XDP512 Data Sheet, Rev. 2.21
Freescale Semiconductor
363