Modicon 984 no talkie, talkie 1

[andz34]

Hello,

My name is Andrew Johnson and i am having a problem with a Modicon 984 controller that will not talk. I have established communication with "A" controller, however, "B" controller cannot be accessed through any of the workstations. There is a status light "COMM Port 2 Active" which is flashing rapidly and continuously on controller "A". Controller B's same light will flash slowly 3 times, and then pause before beginning again. I have no way to figure out what this status light is trying to tell me. I was wondering if anyone had more experience than me troubleshooting Modbus comm.

 

[amorrison]

This question might be too "practical" for most engineers.

Suggest you post to

http://groups.google.ca/group/sci.engr.control/topics?gvc=2&hl=en

 

[spook6869]

I don't know if this is helpful...

On many Compact 984, the second DB9 port is the Modbus Plus port. When Modbus Plus communications are ok, the led next to this port flashes continously and rapidly. When Modbus Plus comms are not good, it blinks in a specific pattern that indiciates a specific problem. Your situation sounds like this.

Three blinks means the controller doesn't see the network. Check to make sure your wiring is ok.

I've only worked with the compact version of the 984. On this model, the second port is clearly labeled as Modbus Plus. There is no blinky diagnostics for the regular serial port (Modbus RTU) that I know of...

Good luck.

 

[cobraman]

You may want to cheek your dip switch settings. Meaning that they can not be alike. By that I mena there can only be 1 node 0 and 1 node 1 ect...

 

[andz34]

Thanks Spooks and cobraman,

The DIP Switches are set for each controller to have its own address. There is a problem with the blue hose between them. I just needed help with the diagnostics of the controller, because I knew the flashing light was trying to tell me something was wrong. We just had no quick way to get the manual to look these diagnostics up. Anyways, thanks for your help!!!