MicroLogix Modbus RTU to Chessel 5180V Recorder Problem

[45bob]

I am trying to read values from a Chessel 5180V Recorder into a MicroLogix 1500 PLC using Modbus RTU. Channel 1 of the 1500 is set up as Modbus Master, the Recorder is Modbus Slave (Node 2). For starters, I tried to read an IEEE Floating Point value of Recorder Channel 1 PV by using the MSG instruction in the PLC (Read Holding Register). Set up as a 32 Bit element, the destination for the value in the PLC is F8:0. I get an error message that there is something wrong in the packet sent from the Recorder which the PLC cannot process. Comm speeds and configuration for both instruments are set the same.

When I try to read the same Rcdr Channel 1 PV from its integer value register, I do get a number in my N7:15 destination, but it's not correct, because the recorder is an unsigned integer value, but the ML1500 integers are signed +/- 32,767.

Ultimately, I do want to read the floating point values. Has anyone used an Allen-Bradley Modbus RTU to talk to a Chessel 5180V successfully?

 

[gcaudill]

The values from the Recorder may be in Hex, even when reading the Floating Point registers. Thus, going directly to the F8:0 register is not possible?