ML1400 - modbus slave help

[rQx]

Hi!

I have a ML1400 that our customer wants to communicate with. I'm very unfamiliar with RSLogix and Allen Bradley programming overall but I think I have done this the correct way. Maybe some of the more experienced user here can have a look if I have made some rookie mistakes? I will test this as far as I can before I deliver the cabinet to.

All suggestions and critisism is appreciated

/Tim

 

[rQx]

Anybody?

I have changed the heartbeat function so it functions correct.

 

[Bullzi]

Are you using TCP or RTU? Can you post your Channel Configuration with the Modbus Data Table Configuration? That would help us see how you have it set up.

 

[harryting]

Not enough there to tell what's going on. I see stuff going to B file but how's that tied to your modbus (serial) port? Maybe post your ladder and I'll try to dig in more.

 

[rQx]

I'll try to get some more info for you tomorrow. Basicly it's not the communication I'm after. It's the way of transferring my values into the B and N files, how to use the modbus registers correctly.

I use Modbus TCP

Contacts B30
Coils B31

Input register N32


As it is now I'm transferring I/Os straight to output B30:X/X
and copy my analog values from I to B30:X
and moving some integers to N32:X
I recieve four bits N31:0/X

I have tested the modbus and it works and I can recieve information, I'm just wondering: Is this the "correct" way of doing it? There arent anything I'm missing?

For example: The analog values, I copy them to B30:4, B30:5 and B30:6. Will the master be able to read them? Do they Read Coil 00065, 00081 and 00097 and specify word and get the whole analog value. Or do I have to do something else here?

Sorry for the stupid questions but I've never worked with modbus before.

 

[bernie_carlton]

Why don't you copy the analog values to N32.xx also? The might be easier to read by the Modbus client.

 

[Bullzi]

I am sure you have it set up right if it is working. To know how you have things set up it would help if you can post a screen shot like this.

 

[rQx]

I didn't know you could do that (not familiar with RA software) since it is in WORD form i guessed that the suitable modbus register was Contact. You're saying that I can use Copy instruction and copy the input value straight to my Input register in INT form?

 

[rQx]

I am sure you have it set up right if it is working. To know how you have things set up it would help if you can post a screen shot like this.

I'll take the screenshot tomorrow at work and post. I'm at course the whole day but I'll have some time in the evening to take it.

 

[Bullzi]

It depends on the type of analog data. If it is 16 bit data (INT) you can copy it over. If it is floating point data you will have to use the Copy Word (CPW) command. The source would be your analog data and the Dest would be N32:x and length of 2.
Then the Modbus Master would read the 2 INT words to get the floating point data.

 

[rQx]

It depends on the type of analog data. If it is 16 bit data (INT) you can copy it over. If it is floating point data you will have to use the Copy Word (CPW) command. The source would be your analog data and the Dest would be N32:x and length of 2.
Then the Modbus Master would read the 2 INT words to get the floating point data.

Yes I think it is a 16bit word, so a copy would do the trick then, thanks alot for that tip. Sure is more straight forward to read that from the input register.