We recently upgraded a GE Fanuc 9030 to an Emerson RX3i with a modbus TCP connection to a GE Mark VIe. The logic and addressing remains the same from the old program to the new (it's in fact a near direct conversion), but now we are now getting a bad data error at the Mark VIe. We've confirmed the RX3i is connecting to the Modbus Master and that it is transmitting the Modbus points, but for whatever reason the Mark VIe isn't recognizing the data.

The Modbus address tables between the 9030 and RX3i are the same except that the %Q and %I tables have a larger range. We're only polling a small number of points from the PC, so not sure if this could what is causing the problem or not.

We also can monitor the PSCA in the Mark VIe, and all the points are in holding registers so none of the addressing seems to line up with what we're expecting to see. Is there an additional configuration that would tie the PLC Modbus addresses to the Holding Registers in the Mark VIe?

 

I'm not familiar with this equipment, but could this be caused by the common "off by 1" addressing issue in Modbus?

Perhaps the 9030 used 0-based register addressing and the RX3i uses 1-based, or vice-versa. Have you tried adding 1 to, or subtracting 1 from, the RX3i's register addresses?

 

We recently upgraded a GE Fanuc 9030 to an Emerson RX3i with a modbus TCP connection to a GE Mark VIe. The logic and addressing remains the same from the old program to the new (it's in fact a near direct conversion), but now we are now getting a bad data error at the Mark VIe. We've confirmed the RX3i is connecting to the Modbus Master and that it is transmitting the Modbus points, but for whatever reason the Mark VIe isn't recognizing the data.

The Modbus address tables between the 9030 and RX3i are the same except that the %Q and %I tables have a larger range. We're only polling a small number of points from the PC, so not sure if this could what is causing the problem or not.

We also can monitor the PSCA in the Mark VIe, and all the points are in holding registers so none of the addressing seems to line up with what we're expecting to see. Is there an additional configuration that would tie the PLC Modbus addresses to the Holding Registers in the Mark VIe?

Would prefer the supplier to fix it. Usually it's the upgrade team / company's scope to ensure that everything is intact & working as expected.

If you dont know what you are doing with the Memory address (Reading OR Writing a WRONG MEMORY Address), it could lead to a unexpected disaster or safety critical issue.

It could be issue with LSB vs MSB or issue with Byte offset (Which need to correctly manually by getting in touch with the respective vendor and get the correct memory mapping.