25.6.6 Timer1 Gate Event Interrupt
When Timer1 gate event interrupt is enabled, it is possible to generate an interrupt upon the completion of a gate event. When the falling edge of GVAL occurs, the TMRxGIF flag bit in one of the PIR registers will be set. If the TMRxGIE bit in the corresponding PIE register is set, then an interrupt will be recognized.
The TMRxGIF flag bit operates even when the Timer1 gate is not enabled (the GE bit is cleared).