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Reading Data from UDC2500 in Labview.
Communicating with a UDC 2500 PLC via Labview OPC


I am trying to read the data in Labview from Honeywell controller UDC 2500 via Ethernet and OPC. Has anyone been able to do it successfully? I am not sure what I need to do on the Labview to talk to the controller?

Can someone throw some light on it?

Quick response is appreciated.


Yes, I've done it. The UDC works and works fairly reliably for PV/SP/Output reads and the occasional setpoint write.

Most variables are mapped to both integer and Floating Point (FP) registers. The setup allows one to choose an FP format on the controller (the two common FP formats are FP B and FPLB). The UDC is always a slave/server.

Several Gotchas:

Throw out the Modbus manual section in the UDC 2500 product manual 51-52-25-127. That information is for using Modbus as a configuration tool, writing to memory locations for configuration. The register/addressing refers only to its use with Function Codes 20/21 (decimal), which most masters do not support.

The Modbus slave register/address map/table and other Modbus infor that you need is in the Modbus RTU Serial Communications User Manual. 51-52-25-66, the latest edition is rev T.

There is no ModbusTCP manual, the RTU manual applies to both hardware buses. The register/address assignment is identical, whether RTU or TCP.

Pay attention to the read limits and specifically the write limit (on page 12 [18pdf], which is one word/register per write transaction, even with FC16 (10hex). These are single loop controllers, not Windows PCs.

Big Gotcha ! !
The Ethernet card's IP address can not be configured from the UDC keyboard. It's IP address can only be changed with Honeywell's Process Instrument Explorer (PIE) software. A Honeywell distributor might change it for you.

UDC2500's have been out now for 13-14 years. In the early years, the first couple firmware versions on ROM on the Ethernet cards were sorely dysfunctional. Random high values would appear in the reply data and frequently. It was sorted out, but it was bad firmware.

Avoid writing the same data, on at intervals, because the non-volatile memory can only take about 10,000 writes. Write the setpoint, then leave it, until it needs to be changed. Don't re-write the same SP every second or it'll crash sooner than later.

As to NI's software, I don't have a clue, I've never used it. But a quick jaunt on their web revealed a tutorial for Modbus:

Connect Labview (master) to a PLC

NI Introduction to Modbus

Modbus Library for Labview