bm_engineering Posted November 28, 2013 Report Share Posted November 28, 2013 I was just playing with the V130 Modbus TCP slave communication. I set everything up and connected through my simulator. Reading holding registers worked fine. However, when I switched to reading coils, I got timeouts. With a bit of playing, I discovered that if I asked for 7 or fewer addresses it worked fine. At 8 or more I got timeouts. However, I could shift the address range up by 7 and ask for 7 more and it worked fine. It is not the addresses, just the number of multiple coils requested (one byte?). This is far below the Modbus spec for multiple addresses. I got the same result on a V350. I have not found this documented anywhere, but it appears to be the intended operation. I don't use the Modbus coils very often, so I may have just never noticed it. Have others experienced this limit? Quote Link to comment Share on other sites More sharing options...
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