Modbus TCP Cannot Read Coil
I'm trying to read data from an analyser over Modbus TCP into 800xa AC800M. Comms to the unit is working correctly and all registers are reading correctly.
However I cannot read from Coils. I have tried a number of different start address formats but without success. See attched for both the modbus map from the device and a screenshot from my code. You can see the other reads working but the coil giving an error.
Any help on this is much appreciated!
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Hi Rob / Harsha,
I've tried connecting a boolean32 with the address %QX10#2000 with the same result - error 4903.
Is it definitely QX I should be using to read this coil? I have tried with offsets too with no success.
To summarise here is what I've tried:
Trying to read value of "Coils (Read) : Address 2000"
%QX10#2000 with Bool16 / Bool32 connected gives Error 4903
%IX10#2000 with Bool16 connected gives Error 4902
%QX10#1999 with Bool16 connected gives Error 4903
Thanks for your help so far.
I think I've solved this now - I've connected a single bool type to the output of the function block and it worked using the QX address. As it happens there is no offset used on this device - all addresses are working as per the modbus map.
Thanks for your help Harsha and Rob.