20.2.1 Sync and Trigger Operation

In both 16-bit and 32-bit modes, the timer can also function in either synchronization (“sync”) or trigger operation. Both use the SYNC[4:0] bits (CCPxCON1H[4:0]) to determine the input signal source. The difference is how that signal affects the timer.

In sync operation, the timer Reset or clear occurs when the input selected by SYNC[4:0] is asserted. The timer immediately begins to count again from zero unless it is held for some other reason. Sync operation is used whenever the TRIGEN bit (CCPxCON1H[7]) is cleared. SYNC[4:0] can have any value, except ‘11111’.

In trigger operation, the timer is held in Reset until the input selected by SYNC[4:0] is asserted; when it occurs, the timer starts counting. Trigger operation is used whenever the TRIGEN bit is set. In Trigger mode, the timer will continue running after a trigger event as long as the CCPTRIG bit (CCPxSTATL[7]) is set. To clear CCPTRIG, the TRCLR bit (CCPxSTATL[5]) must be set to clear the trigger event, reset the timer and hold it at zero until another trigger event occurs. On dsPIC33CK256MC006 family devices, trigger operation can only be used when the system clock is the time base source (CLKSEL[2:0] = 000).