MSG instruction SLC 5/04 to PLC-5

Hi all,

I'm venturing into new territory, programming MSG instructions for the first time

What I'm wanting to do is send an alarm bit from a SLC to a PLC-5 over DH+ to trigger an alarm in the 5, and then when the alarm is acknowledged by a push button on the machine with the PLC-5, send an acknowledge request back to the SLC.

After reading the help files, and instruction set manuals for both processor types, I think I understand how to set the parameters, but I've still got a really dumb question: On a MSG write from 500 to 5, do you have to have a corresponding MSG read instruction on the target device (5), and vice versa?

Also, I'm wondering if it would be better to only trigger the MSG instructions when an alarm condition exists, or rather just cycle the transfers continuously. I only want to transfer one word at a time(say N7:0), which from the 500 to 5 would be a 1 when in alarm and 0 when clear, and on the 5 to the 500 the word (call it N7:1) would be a 1 when the alarm acknowledge request was set, and then reset to 0 upon completion of MSG transfer.

I played with it some today at work, but didn't have much luck. After more studying, I see several things I was doing wrong, but I'm still unclear about whether the instructions have to be paired on the target device.

Any help/advice would be much appreciated.

Thanks,
Dustin

You do not need a matching Message Instruction in the other PLC, it will all automagically happen. In general, it is safer to do Read Messages at both ends, but that is not always possible depending on the mix of Processors.

It would be fine to trigger it on event, but make sure that you only trigger the message once per state change.

Messages can screw up, so some error detection to re-trigger the message would be good.

Hopefully Ken Roach will chime in, he is the Guru when it comes to AB Communications.

Stu...

Simple answer NO. in the message box make sure that the target address is set in the recieving controller. If your sending bit SLC 500 B3:1/12 to PLC 5 B3:2/13 make sure that B3:2/13 is in the program for the PLC 5.

sthompson said:

You do not need a matching Message Instruction in the other PLC, it will all automagically happen. In general, it is safer to do Read Messages at both ends, but that is not always possible depending on the mix of Processors.

Click to expand...

Awesome! That should eliminate quite a few of the headaches right there.

It would be fine to trigger it on event, but make sure that you only trigger the message once per state change.

Messages can screw up, so some error detection to re-trigger the message would be good.

Click to expand...

Ok, great, I think I will have a trigger bit latch in on the 500, that will be part of the MSG'd word, and have that bit unlatch when /DN of MSG is true. If /ER is set, then OTU the /EN instruction so MSG can re-transmit.

Then when Alarm Ack is pressed on the 5, latch a bit in the other MSG'd word and have it trigger the same process. I guess that would be a Write on both ends, though. Have to play with some more, I suppose.

Thanks for the help!

:site:

I am sure you have looked at it, but for reference Chapter 12 of the following Manual has the information on the Message Instruction.

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1747-rm001_-en-p.pdf

Stu....

sthompson said:

I am sure you have looked at it, but for reference Chapter 12 of the following Manual has the information on the Message Instruction.

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1747-rm001_-en-p.pdf

Stu....

Click to expand...

Yes, I've got it, thanks though.

When trying to do this earlier, I was getting this error code on the 500 side:

EEH Target Node responded with: Command cannot be executed.

Click to expand...

Could that be caused by having another instruction on the 5 trying to read the same data that the 500 was trying to write?

(I would post code, but not sure how sternly it would be frowned upon)

Just to make it a little more confusing, because there is a small amount of data to transferred ,you have another option. "Global Staus Words" ( SLC) and "Global Status Flags" (PLC5). These transfer information across the DH+ network without a message instruction. See PDF's below for more info on them.

Mickey said:

Just to make it a little more confusing, because there is a small amount of data to transferred ,you have another option. "Global Staus Words" ( SLC) and "Global Status Flags" (PLC5). These transfer information across the DH+ network without a message instruction. See PDF's below for more info on them.

Click to expand...

Not that I needed any help in THAT regard lol. I actually read about the global status flags in another thread earlier, and while that is a tempting "quick fix", I'd like to get a handle on using the MSG instruction, since it has such a wide variety of applications.

Thanks for the info.

Cheers,
Dustin

bmacattack33 said:

When trying to do this earlier, I was getting this error code on the 500 side:

Could that be caused by having another instruction on the 5 trying to read the same data that the 500 was trying to write?

(I would post code, but not sure how sternly it would be frowned upon)

Click to expand...

If you mean posting the PLC Code here, that is no problem as long as you Zip it first. If you mean your companies policy, you will have to enquire.

As to your error, make sure you have the right destination path. Is it on the local DH+ Network to the SLC, or do you need more complicated routing? Make sure the Source and Destination Address exist in their respective PLCs, and are available for the Messaging.

Stu....

bmacattack33 said:

When trying to do this earlier, I was getting this error code on the 500 side:

Could that be caused by having another instruction on the 5 trying to read the same data that the 500 was trying to write?

(I would post code, but not sure how sternly it would be frowned upon)

Click to expand...

No, it couldn't.

I'm agree with other guys, you've to double check message configuration, and posting here your programs would help.

Beside that, I remember that using a PLC-5 processor,you can also specify privileges to protect data files from write access on a DH+ link. Try to check using RSlogix 5 inside the folder Passwords and Privileges, Administer Privileges, Feature Privileges... Physical Write and Read are the assignments you're interested in.
Maybe not the case, but checking it doesn't require too much time.

- fuzzy logic

After my brain decided to wake up, I wonder if I've found an answer for you...

In the write message block, inside RSLogix500, you've to select as "TARGET DEVICE" PLC5, probably you've used 500CPU there... ?!
It could happen as it is the default setting...

- fuzzy logic

Morning, guys. I'll have to look at this again when I get to work and see where I'm at.

sthompson said:

As to your error, make sure you have the right destination path. Is it on the local DH+ Network to the SLC, or do you need more complicated routing? Make sure the Source and Destination Address exist in their respective PLCs, and are available for the Messaging.

Click to expand...

It's on a local network, and the addresses definitely exist, but what do you mean "available" for messaging? Data type, maybe?

Fuzzy Logic said:

In the write message block, inside RSLogix500, you've to select as "TARGET DEVICE" PLC5, probably you've used 500CPU there... ?!
It could happen as it is the default setting...

Click to expand...

No, definitely had target device set as PLC-5.

No, it couldn't.

I'm agree with other guys, you've to double check message configuration, and posting here your programs would help.

Beside that, I remember that using a PLC-5 processor,you can also specify privileges to protect data files from write access on a DH+ link. Try to check using RSlogix 5 inside the folder Passwords and Privileges, Administer Privileges, Feature Privileges... Physical Write and Read are the assignments you're interested in.
Maybe not the case, but checking it doesn't require too much time.

Click to expand...

I'll have to double check to be sure, but I know the PLC-5 isn't password protected, and I believe it's using MSG instructions to other nodes, so I don't think the Physical Write and Read are protected either.

Thanks for the responses guys. I'll check back in after I've messed with it for awhile, let you guys know how it went.

Cheers,
Dustin

May you please add the PLC-5 model you're messaging to ?
I mean purchase code, series firmware etc.

- fuzzy logic

fuzzy logic said:

May you please add the PLC-5 model you're messaging to ?
I mean purchase code, series firmware etc.

- fuzzy logic

Click to expand...

Sorry for the lateness of reply.

PLC 5/60
Series B
Revision G

I was able to get the transfer to work by doing both Read and Write on the SLC.

For some reason, If I try to read or write from the PLC-5, I don't get any error codes, but the .en just stays on, even if I unlatch the .co bit in the rung prior to MSG instruction. So the message just runs continually, never sets the .dn, .to, or .er bit, but it never moves any information either. I tried using Typed Read, Typed Read to SLC, and Logical Read to SLC, it all behaves the same regardless.

There is quite a bit of traffic on the PLC-5, it sort of acts as the hub of the process, so that may have something to do with it, but I thought if there was too much traffic on a node, then the MSG should set a .WQ bit?

So that's where I'm at, thanks again to everyone for their help :nodi:

Cheers,
Dustin