Logix 500 Modbus Table Creation?

[TimD]

Hello,

I have a need to read data from a Modbus Slave. The slave is a Davis Weather Station with Modbus interface card. I have it all hooked up to Ch 0 on my ML1100 and Ch 0 is configured as Modbus Master, 9600 baud, etc...

The Logix help file says I need to create a Modbus table of type Int or Bool. I looked at the obvious Data File area, but see no option for type Modbus. The help file says there is a "Create..." dialog, but I can't find it.

If anyone has set up Modbus slaves before, please chime in here. I have never done it before.

Many Thanks!

Tim

 

[bernie_carlton]

If you are the master then you don't need to set up the Modbus table. That is only used when an outside unit interrogates your ML1100. Since you are the master there can be no other.

 

[TimD]

Hi Bernie,

Thanks. I think I may have figured it out. The one-page instruction page gave few 'clues'. I ended up making a data file of ints and coupled a message file and block to them. The MSG block reads 30 int values and stores them into the message file.

I hope that is how this is supposed to work!

Tim

 

[bernie_carlton]

Each MSG command gets its own area (the MG file member) to keep track of its communication. In the setup screen the 'Data Table Address' is simply the address where you want the command to put the stuff you are asking for. It obviously must be big enough to hold what you are requesting.

Oh, make sure you selected MODBUS RTU Master for Channel 1.

If you select MODBUS RTU slave then - since the Micrologix doesn't naturally have MODBUS registers - you assign certain Integer files and Bit files as 'pseudo MODBUS' tables. But you aren't doing this.