Limit on number of simultaneous GET_X instructions in a S7-300?

I need to transfer several hundred bytes of data from two different S7-300 PLCs to a central S7-300 PLC over an MPI network. I am using the GET_X instruction to transfer the data.

Since the size of the data being transferred is more than the maximum 76 byte limit of the GET_X instruction I need to use several GET_X calls to get the data. Can I invoke more than one GET_X call to the same remote PLC at the same time or will I have to make one call, wait for it to complete, make the second call etc.

Is GET_X the best way to do the job. I can find very little documentation on this instruction.

MPI limitation either Profibus/Profinet

for your reference


http://www.plctalk.net/qanda/showthread.php?t=56871

http://www.plctalk.net/qanda/showthread.php?t=70000

http://support.automation.siemens.c...lib.csinfo&lang=en&objid=20982954&caller=view

https://a248.e.akamai.net/cache.aut...zYyMwAA_49450152_FAQ/PUT_GET_Sequencer_en.pdf

Options for communications via MPI

If you need large data exchange probably the best way, as osmanmom said, is SFB15 "PUT"/SFB14 "GET"

Great references from other responses. If it were me, I would sequence them (wait for each to complete) since that allows you to send an unlimited amount of data. There are strict limitations about the number of simultaneous puts/gets that are cpu-dependent - so i just avoid that whole issue and do them sequentially. Is still quite fast that way: each GET completes in one or 2 scans, if I recall (not dead sure about that, lousy memory, and my use was over Profinet - test it).