MC9S12G Family Reference Manual Rev.1.27
NXP Semiconductors 623
Chapter 19
Pulse-Width Modulator (S12PWM8B8CV2)
19.1 Introduction
The Version 2 of S12 PWM module is a channel scalable and optimized implementation of S12
PWM8B8C Version 1. The channel is scalable in pairs from PWM0 to PWM7 and the available channel
number is 2, 4, 6 and 8. The shutdown feature has been removed and the flexibility to select one of four
clock sources per channel has improved. If the corresponding channels exist and shutdown feature is not
used, the Version 2 is fully software compatible to Version 1.
19.1.1 Features
The scalable PWM block includes these distinctive features:
• Up to eight independent PWM channels, scalable in pairs (PWM0 to PWM7)
• Available channel number could be 2, 4, 6, 8 (refer to device specification for exact number)
• Programmable period and duty cycle for each channel
• 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
• Up to 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
19.1.2 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.
Wait: The prescaler keeps on running, unless PSWAI in PWMCTL is set to 1.
Freeze: The prescaler keeps on running, unless PFRZ in PWMCTL is set to 1.
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