Time Loop synchronization with scan engine delayed in PXI Real-Time

[cvbnvbcnelm]

Hi

I am working on PXI real time system with EtherCat  connected to NI9145 chassis. an analog input is read from NI-9215. In the PXI a Time-loop sync with scan engine was used. scan engine frequency is 1kHz. when I measure the time execution of this time Ioop, I expect that it must be 1000 micro Sec. It is almost Ok. but some times, a lag was happened. this lag is from scan engine. but I don't know why? coud somebody help me why this happen? or guide me to read a referenc?

thanks.

[ZYOng]

How can you be sure that the lag is from the scan engine? Is there anything else other than the scan engine node in the timed loop?

Can you post the code for us to understand better?