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 @ fOP = 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
PERIOD = 8 X (PWM CLOCK PERIOD)
PWM = 0
PWM = 1
PWM = 2
PWM = 3
PWM = 4
Figure 12-4. Center-Aligned PWM (Positive Polarity)
Data Sheet
132
MC68HC908MR32 • MC68HC908MR16 — Rev. 6.0
Pulse-Width Modulator for Motor Control (PWMMC)
MOTOROLA
FREESCALE [ Freescale ]
