float from panelview to micrologix 1400 over modbus

Hemlock

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Join Date
Mar 2014
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Central FL
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20
I've run into a problem with my Panelview C600 and modbus comms to a Micrologix 1400. I can set up a numerical entry on the screen, and it works fine, since the HMI passes info into an integer (holding) register on the PLC. If I set up a floating point entry, it rounds to input to the nearest integer in the holding register. I can put a float into the touch screen, but I can't get it to the PLC. Is there an easy way around this? I have to stay with Modbus for comms.

Thanks for your help.
 
Last edited:
Before I spend any time trying to figure this out, you've got to give me a good reason why you would use Modbus between two devices that are designed, tested, advertised, documented, and sold to work together with their native protocols.
 
Well Ken, long story short it isn't my project from the start. The other channels are in use, and Modbus is what I have available. Like I said in my first post, not my choice.

I could put the units into something that effectively shifts the decimal to the right, but that seems less than elegant. It also seems less than intuitive for the intended users.

If there isn't a simple way to do this I will push again for using a different comms channel. That will require additional hardware as well as changing a rather entrenched way of doing things. Both are not trivial, hence my asking for help here.
 
I don't understand... it's impossible for you to have a communication channel on a MicroLogix that can both be connected to the PanelView Component and only be configurable for Modbus RTU Slave.

If you have a serial port that's configured for Modbus RTU Slave (Channel 0 or Channel 2), then it can have only one Modbus RTU Master connected. Therefore you could change that serial port back to native DF1 protocol.

Unless you've got some unusual network gateway architecture going on to accommodate somebody packing 10 pounds of controler into a 5 pound bag.

Packing a 32-bit floating point value into adjacent Modbus RTU Holding Registers is a classic Modbus challenge, but I don't have the PanelView Component driver experience to advise you on how to do it.
 
Ken, I may be expressing things incorrectly. I'll try bouncing it off my roadblock on the other side and see if I can get around the Modbus there.
 

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