MC908MR16CFUE Datasheet, PDF (120/282 Pages) Freescale Semiconductor, Inc – On-chip programming firmware for use with host personal computer, Clock generator module (CGM)

Pulse-Width Modulator for Motor Control (PWMMC)
12.3 Timebase
This section provides a discussion of the timebase.
12.3.1 Resolution
In center-aligned mode, a 12-bit up/down counter is used to create the PWM period. Therefore, the PWM
resolution in center-aligned mode is two clocks (highest resolution is 250 ns @ f_OP = 8 MHz) as shown in
Figure 12-4. The up/down counter uses the value in the timer modulus register to determine its maximum
count. The PWM period will equal:
[(timer modulus) x (PWM clock period) x 2].
UP/DOWN COUNTER
MODULUS = 4
PWM = 0
PWM = 1
PWM = 2
PERIOD = 8 X (PWM CLOCK PERIOD)
PWM = 3
PWM = 4
Figure 12-4. Center-Aligned PWM (Positive Polarity)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor