Справочник Пользователя для Motorola MC68HC908MR16
Pulse-Width Modulator for Motor Control (PWMMC)
Timebase
MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
Advance Information
MOTOROLA
Pulse-Width Modulator for Motor Control (PWMMC)
141
9.4 Timebase
This section provides a discussion of the timebase.
9.4.1 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
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
. 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].
Figure 9-3. Center-Aligned PWM (Positive Polarity)
UP/DOWN COUNTER
MODULUS = 4
PWM = 0
PWM = 1
PWM = 2
PWM = 3
PWM = 4
PERIOD = 8 X (PWM CLOCK PERIOD)