Ok lets take it from the top. First in the Micro820 Modbus mapping - Your count_value needs to be at address 400001 this is where holding registers are mapped in Modbus.
In the configuration for the Modbus TCP driver under advanced properties check “Reverse Word Order”. The rest of the default settings should be fine.
Now go the the “Addresses” for the Modbus TCP driver
Reset_Count is a coil and Count_Value is a holding register. The Prefixes I used below are arbitrary , call them what you want but they will be used in your Tag.
Finally define your tags, using my example I called the Modbus TCP Device “Line5” so the OPC Item Paths for your tags will be:
Reset_Count = ns=1;s=[Line5]DO1
Count_Value = ns=1;s=[Line5]Dint1
Notice the prefixes we defined under Addresses.
This should get you up and running. I left out the explanation of the why’s for a couple of these steps to keep this short and just get you going. Let me know if you want more information or run into issues.