Advance Information MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
164 Pulse-Width Modulator for Motor Control (PWM MC) MOTOROLA
Pulse-Width Modulator for Motor Control
The filtered fault pin’s logic state is reflected in the resp ective FPINx bit .
Any write to this bit is overwritten by the pin state. Th e FFLAGx event bit
is set with each rising edge of the respective fault pin after filtering has
been applied. To clear the FFLAGx bit, the user must write a 1 to the
corresponding FTACKx bit.
If the FINTx bit is set, a fault condition resulting in setting the
corresponding FFLAG bit will also latch a CPU interrupt request. The
interrupt request latch is not cleared until one of these actions occurs:
The FFLAGx bit is cleared by writing a 1 to the corresponding
FTACKx bit.
The FINTx bit is cleared. This will not clear the FFLAGx bit.
A reset automatically clears all four interrupt latches.
If prior to a vector fetch, the interrupt request latch is cleared by one of
the actions listed, a CPU interrupt will no longer be requested. A vector
fetch does not alter the state of the PWMs, the FFLAGx event flag, or
FINTx.
NOTE: If the FFLAGx or FINTx bits are not cleared during the interrupt service
routine, the interrupt request latch will not be cleared.
9.7.1.3 Manual Mode
In manual mode, the PWM(s) are disabled immediately once a filtered
fault condition is detected (logic high). The PWM(s) remain d isabled until
software clears the corresponding FFLAGx event bit and a new PWM
cycle begins. In manual mode, the fault pins are grouped in pairs, each
pair sharing common functionality. A fault condition on pins 1 and 3 may
be cleared, allowing the PWM(s) to enable at the start of a PWM cycle
regardless of the logic level at the fault pi n. See Figure 9-28. A fault
condition on pins 2 and 4 can only be cleared, allowing the PWM(s) to
enable, if a logic low level at the fault pin is present at the start of a PWM
cycle. See Figure 9-29.
The function of the fault control and event bits is the same as in
automatic mode except that the PWMs are not re-enabled until the
FFLAGx event bit is cleared by writing to the FTACKx bit and the filtered
fault condition is cleared (logic low).