Help understanding msg in rslogix 500

[Mickey]

Why don't you post both programs and tell us which PLC is the sending unit and which is the receiving unit. Zip the files first.

 

[OkiePC]

Okay, what is your control block?
Label it's bits. I like to use short symbols somtimes, so then you can use MSG1_ER instead of Nxx:yy/13 (or whatever bit it is I memorize nothing except where to find things).

Then, we can find good examples of how to handle the type of message you want to test, how to trigger it, see that it is done, deal with errors, etc.

I was going to write up an example with freeware500 but it only supports the 1100 with MG file based control word and is a bit of a different animal, but I am sure if you search Ken Roach and MSG you will get some leads.

http://www.plctalk.net/qanda/showthread.php?t=61499&highlight=MSG+message

 

[Bit_Bucket_07]

it is nearly midnight and i still cant get my head around this msg instruction, the read write instruction is already being used...

It is important to understand that a single MSG function, while capable of either reading or writing data, does not do both. I have assumed that your two PLCs are actually connected to one another and that the existing MSG function actually works. Even if it does, it will not support what you want to do if the existing MSG instruction is not transferring data in the direction in which you want your new data transfer to take place.

 

[stu]

Bit_bucket u might have hit the nail on the head. , if I am sending the signal to a plc I'm writing is that right ? I will attach the program soon thanks

 

[Bit_Bucket_07]

Bit_bucket u might have hit the nail on the head. , if I am sending the signal to a plc I'm writing is that right ? I will attach the program soon thanks

Yes. You may transfer data in either direction from either PLC by choosing whether the MSG instruction executes a "read" command or a "write" command.

 

[stu]

i am trying to send an alarm from plc1 (sender) there is a write in lad 2 rung 13, i put lad3 rung16/17 to test input.
plc2 is where we want the alarm bit ,lad 2 rung 42 there is a read instruction?
can you give me some understanding becuase im not getting it at the moment

 

[ianingram]

I just had a quick look at both of your programs..

In the Sender PLC1, the address N36:0/5 is at 0.
In the Receive Alarm PLC2, the address N126:0/5 is also 0.

Can you set the alarm in the Sender PLC? That way we can tell if the message is getting across.

Note that in PLC1, N36:0/1 is 1 and in PLC2, N126:0/1 is also 1, this indicates to me that these values are being transferred ok