Timer1 Gate Toggle Mode

When Timer1 Gate Toggle mode is enabled, it is possible to measure the full-cycle length of a Timer1 Gate signal, as opposed to the duration of a single-level pulse. The Timer1 gate source is routed through a flip-flop that changes state on every incrementing edge of the signal. See the figure below for timing details.

Timer1 Gate Toggle mode is enabled by setting the GTM bit. When the GTM bit is cleared, the flip-flop is cleared and held clear. This is necessary to control which edge is measured.

Important: Enabling Toggle mode at the same time as changing the gate polarity may result in indeterminate operation.
Figure 1. Timer1 Gate Toggle Mode