SCTimer/PWM Clearing the prescaler

When enabled by a non-zero PRE field in the Control register, the prescaler acts as a clock divider for the counter, like a fractional part of the counter value. The prescaler is cleared whenever the counter is cleared or loaded for any of the following reasons:

  • Hardware reset
  • Software writing to the counter register
  • Software writing a 1 to the CLRCTR bit in the control register
  • an event selected by a 1 in the counter limit register when BIDIR = 0

When BIDIR is 0, a limit event caused by an I/O signal can clear a non-zero prescaler. However, a limit event caused by a Match only clears a non-zero prescaler in one special case as described SCTimer/PWM Match vs. I/O events.

A limit event when BIDIR is 1 does not clear the prescaler. Rather it clears the DOWN bit in the Control register, and decrements the counter on the same clock if the counter is enabled in that clock.