Pulse-Width Modulator for Motor Control (PWMMC)
Control Logic Block
MC68HC908MR16/MC68HC908MR32 — Rev. 4.0 Advance Information
MOTOROLA Pulse-Width Modulator for Motor Control (PWMMC) 173
automatically cleared after the new values are loaded or can be
manually cleared before a reload by writing a 0 to it. Reset clears
LDOK.
1 = Load prescaler, modulus, and PWM values.
0 = Do not load new modulus, prescaler, and PWM values.
NOTE: The user should initialize the PWM registers and set th e LDOK bit before
enabling the PWM.
A PWM CPU interrupt request can still be generated when LDOK is 0.
PWMEN — PWM Module Enable Bit
This read/write bit enables and disables the PW M g en er ator and the
PWM pins. When PWMEN is clear, the PWM generator is disabled
and the PWM pins are in the high-impedance state (unless
OUTCTL = 1).
When the PWMEN bit is set, the PWM generator and PWM pins are
activated.
For more information, see 9.8 Initialization and the PWMEN Bit.
1 = PWM generator and PWM pins enabled
0 = PWM generator and PWM pins disabled
9.10.5 PWM Control Register 2
PWM control register 2 (PCTL2) controls the PWM load frequency, the
PWM correction method, and the PWM counter prescaler. For ease of
software and to avoid erroneous PWM periods, some of these register
bits are buffered. The PWM generator will not use the prescaler value
until the LDOK bit has been set, and a new PWM cycle is starting. The
correction bits are used at the beginning of each PWM cycle (if the
ISENSx bits are configured for software correction) . The load freq uency
bits are not used until the current load cycle is complete.
See Figure 9-39.
NOTE: The user should initialize this register before enabling the PWM.