RS422 packets missed when transmitted at repetition rate of 15ms

Hi,

I am trying to send RS422 serial packets using NI PXI 8431/4 module. My goal is to send serial frame repetitively at 15ms interval, but sometime the packets are missing as they don't occur at next 15ms interval.

I have placed serial transmission VI inside a while loop and added a "wait ms" function to set the loop timing to 15ms.

Can you please guide me how to achieve desired repetition interval?

Thanks,

M Mahboob