Freescale Semiconductor MC68HC908MR32 - Manual (Page 121)

Timebase
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor 121
For edge-aligned mode, a 12-bit up-only counter is used to create the PWM period. Therefore, the PWM
resolution in edge-aligned mode is one clock (highest resolution is125 ns @ f
OP
= 8 MHz) as shown in
Figure 12-5 . Again, the timer modulus register is used to determine the maximum count. The PWM period
will equal:
(timer modulus) x (PWM clock period)
Center-aligned operation versus edge-aligned operation is determined by the option EDGE. See 5.2
Functional Description .
Figure 12-5. Edge-Aligned PWM (Positive Polarity)
UP-ONLY COUNTER
MODULUS = 4
PWM = 0
PWM = 1
PWM = 2
PWM = 3
PWM = 4
PERIOD = 4 X (PWM
CLOCK PERIOD)