Reason for placing communication in cyclic interrupt block?

Hi

I am very new to the field of PLC programming. I am programming an anticollision program on a Siemens SIMATIC ET200S.

I have learned that it is common to place the communication part of the program in a cyclic interrupt block (OB35 in my program), but I don't have a clear reason as to why.

Could anyone give me a short explanation as to why I do this?

This is done in order to ensure consistant timing for the communications calls (say, every 10ms for example). If you do this in OB1 then the timing will vary depending on program load. Even using a Timer to trigger the comms doesn't help here because the Timer's accuracy varies depending on program load and resulting execution (cycle) time.