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Modbus Read Holding Registers more than 125




I've been using NI Modbus library for years and I now have PLCs that supports requests of maximum 1024 bytes (512 registers). The classic Modbus maximum register quantity per request is known to be 125 (250 bytes + 6 bytes of overhead). A PLC such as Schneider M580 seems to now accept 500 registers requests (or maybe more but the total is 1024 bytes).


If I try to read 126 registers with NI Modbus library as it is right now, I obviously get error message 3. Is it possible to modify the library to allow request of 500 requests for instance?


I know I could do several request but I'm facing a performance issue and I already know that the quantity of request is the cause. My solution would be to reduce request quantity.


I found that article but I can't find how it works following the instruction :


I joined my test vi.


Thank you!

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