serial comm between micrologix 1100 & compact logix

hi guys,
I am having a problem regarding the communication between a micrologix 1100 & compact logix using the serial port.I have configured a MSG in compact logix & it works fine( the msg is done) , but the data is not transferred from compact to micrologix?
what could be problem?..the communication between the two is established but the data is not transferred!!

If the /DN bit for the MSG instruction becomes true, then the data transfer is definitely complete.

Be certain you do not have another instruction over-writing the data in the MicroLogix.

Also, remember that the MSG instruction executes once each time the rung conditions make a false-to-true transition. To transfer data repeatedly, you need timer or sequential logic to re-trigger the MSG instruction.

still hooked up!!

nothing could possibly overwrite the data as the controller doesnot contain any logic except the one for transfer!!...

Is the MSG instruction in the CompactLogix, or in the MicroLogix ?

Are you reading data, writing data, or both ?

You stated originally that the MSG instruction is in the CompactLogix and that the data does not appear to arrive in the MicroLogix.

Later you said that there is no logic in the MicroLogix "except the one for transfer".

Does this mean you have another MSG instruction in the MicroLogix ?

I can make a couple more guesses:

1. If the /DN bit becomes true after the MSG is enabled, then the data was confirmed to have been transferred.

2. You do not need a MSG instruction "at both ends" to transfer data; use only one Read or Write instruction.

3. MSG instructions need to be re-triggered each time you want them to transfer data. Use sequence, event, or timer logic to re-trigger the MSG instruction.

4. Do not attempt to directly write into the Input or Output data tables of a controller.

can u attach both program backup?

I am sorry for confusing you ken!..but here is what it is like...I have a MSG instruction in compact logix, which transfers data(or supposed to ) in to micrologix.There is no logic written in micrologix.

I checked the processor status of micrologix & it reads "no messages received".However the DN bit of the msg instruction in compact logix is high denoting a successful transfer.

find the attacned programs

Thank you for posting those files.

I assume that the active MSG instruction is in MainProgram, on Rung 9. It triggers once every 4 seconds based on the LIM instruction preceding it.

You have configured the message as a broadcast message.

The "broadcast" selection is why you are getting a /DN bit without data being received; broadcasts cannot, by definition, receive confirmation of data receipt, so the operating system sets the /DN bit when the transmission is complete.

If this link will include only the CompactLogix and the MicroLogix, I recommend using DF1 Full Duplex protocol.

Set the CIP Path to "2, 1".

Reconfigure the CompactLogix system protocol to be DF1 Point-to-Point and set the Error Checking to CRC to match the MicroLogix controller.


If this system is part of a development that will have multiple serial slaves, you need to take a step back and learn about the protocols that support multi-point networks,

thanks ken for the advice, but its not working.
The MSG instruction is now indicating a fault, fault code -16#001f & an extended code- 16#0000-0204.
I am in a soup!

Code 0204 is a simple timeout.

Did you make all the changes I suggested ? If so, post updated programs.

What kind of serial cable is connecting these controllers ?

I am using PMO2 cable to connect the twoc controllers.
Find the attached programs.

Please be specific about which MSG instruction you are looking at.

In addition, it would be helpful to post a copy of the RSLogix 5000 program that was saved after the messages had been attempted. This means it might include error data.

There are three MSG instructions in your program.

1. Message 'msg' is in Program 'Analog', Routine 'AnalogScaling'
This MSG is unconditional so it will run only once, despite the fact that you are calling the AnalogScaling routine 49 times with a FOR instruction.

It should move the value of the tag "transfer" (value = 0) into N7:0 on the CompactLogix.

2. Message 'msg_write' is on Rung 6 of MainRoutine in MainProgram, but it is preceded by an AFI instruciton so it will not run.

3. Message 'msg_write1' is on Rung 9 of MainRoutine in MainProgram. It is triggered every 4 seconds.

That message is addressed to write the value of tag 'DIBU[0]' (value = 0) into the MicroLogix data table N20:0.

Data Table N20 does not exist in the MicroLogix ! Either create that data table or re-address the MSG instruction.

Also, I recommend setting the CIP Path to '2, 1' instead of '2, 255'. Port 2 is the CompactLogix serial port, and the MicroLogix is configured for DF1 Node 1.

I recommend specifying one data table (like N20) to use for data that's written to the MicroLogix, and another to use for data that's read from the MicroLogix. This reduces confusion when troubleshooting.

In the Serial Port configuration on the CompactLogix, I recommend selecting "No Handshake". With a 1761-CBL-PM02 cable, "Full Duplex" handshaking should work as well, but I would just choose 'No Handshaking' to match the MicroLogix configuration.

You're almost there !

thanks ken!!!

Thank u so much ken!!..it worked out & now the project has been completed.
thanks once again for the help.
can you direct me to any literature , which help me to understand the serial communication & messaging between PLCs in depth?