Pulse-Width Modulator for Motor Control (PWMMC)
Initialization and the PWMEN Bit
MC68HC908MR16/MC68HC908MR32 — Rev. 4.0 Advance Information
MOTOROLA Pulse-Width Modulator for Motor Control (PWMMC) 167
is not reset, and a modulus value of 0 will result in waveforms
inconsistent with the other modulus waveforms. See 9.10.2 PWM
Counter Modulo Registers.
When PWMEN is set, the PWM pins change from high impedance to
outputs. At this time, assuming no fault condition is present, the PWM
pins will drive according to the PWM values, polarity, and dead-time.
See the timing diagram in Figure 9-31.
Figure 9-31. PWMEN and PWM Pins
When the PWMEN bit is cleared, this will occur:
PWM pins will be three-stated unless OUTCTL = 1.
PWM counter is cleared and will not be clocked.
Internally, the PWM generator will force its outputs to 0 to avoid
glitches when the PWMEN is set again.
When PWMEN is cleared, these features remain active:
All fault circuitry
Manual PWM pin control via the PWMOUT register
Dead-time insertion when PWM pins change via the PWMOUT
register
NOTE: The PWMF flag and pending CPU interrupts are NOT cleared when
PWMEN = 0.
CPU CLOCK
PWMEN
PWM PINS
DRIVE ACCORDING TO PWM
VALUE, POLARITY, AND DEAD-TIME
HI-Z IF OUTCTL = 0
HI-Z IF OUTCTL = 0