G
I have been trying to poll a ModbusTCP Temperature probe from my SCADA system. The mfg uses addresses 49 and 50 for Temp and RH, but they don't seem to be valid Modbus read registers in my mind.
Through some back and forth with the vendor, they assert that addresses 49 and 50 are valid for reading ModbusTCP data.
I thought that valid Modbus read registers must start with a 4XXX so I added the prefix to get the address 40049. Note that when I use address 49 and 50, the data is not valid when I read it, but when I use 40049 I do get the same value as their web page reports. My Modbus interpretation that all addresses that start with 00XXX to actually be coil write commands, not a read.
Can someone explain this address problem?
My actual problem with this device is that my first poll will read the correct value and the second read will always come back as 0, then the 3rd read will be correct and the 4th 0, etc.
What would cause this?
GBrown
Through some back and forth with the vendor, they assert that addresses 49 and 50 are valid for reading ModbusTCP data.
I thought that valid Modbus read registers must start with a 4XXX so I added the prefix to get the address 40049. Note that when I use address 49 and 50, the data is not valid when I read it, but when I use 40049 I do get the same value as their web page reports. My Modbus interpretation that all addresses that start with 00XXX to actually be coil write commands, not a read.
Can someone explain this address problem?
My actual problem with this device is that my first poll will read the correct value and the second read will always come back as 0, then the 3rd read will be correct and the 4th 0, etc.
What would cause this?
GBrown