MC9S12T64 Datasheet, PDF (363/608 Pages) Motorola, Inc – Specification

MOTOROLA
Freescale Semiconductor, Inc.
Pulse Width Modulator (PWM8B8C)
Functional Description
PPOLx=0
PPOLx=1
PWMDTYx
PWMPERx
PWMDTYx
PWMPERx
Period = PWMPERx*2
Figure 64 PWM Center Aligned Output Waveform
To calculate the output frequency in center aligned output mode for a
particular channel, take the selected clock source frequency for the
channel (A, B, SA, or SB) and divide it by twice the value in the period
register for that channel.
• PWMx Frequency = Clock (A, B, SA, or SB) / (2*PWMPERx)
• PWMx Duty Cycle (high time as a% of period):
– Polarity = 0 (PPOLx=0)
Duty Cycle = [(PWMPERx-PWMDTYx)/PWMPERx] * 100%
– Polarity = 1 (PPOLx=1)
Duty Cycle = [PWMDTYx / PWMPERx] * 100%
As an example of a center aligned output, consider the following case:
Clock Source = Bus Clock, where Bus Clock =10MHz (100ns period)
PPOLx = 0
PWMPERx = 4
PWMDTYx = 1
PWMx Frequency = 10MHz/8 = 1.25MHz
PWMx Period = 800ns
PWMx Duty Cycle = 3/4 *100% = 75%
The output waveform generated is shown in Figure 65
Pulse Width Modulator (PWM8B8C)
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MC9S12T64Revision 1.1.1
363