SLC 5/05 Ethernet link to control computer

A simple problem but is there a solution?

I have a VME based control computer running linux that I need to connect to a SLC 5/05 PLC via an ethernet link.

The problem is that I am told that the data protocol used
by the SLC5/05 (MSG command) over TCP/IP is proprietory. It is not
available to third parties. The Ethernet interface on the SLC5/05 is not intended to be used by third party CPUs (such as the VME) to communicate with Rockwell Automation SLCs via TCP/IP.

Does anyone have details of the MSG protocol format to allow TCP/IP connections from third party computers over Ethernet?

I think the SLC 5/05 Ethernet implementation is just DF1 wrapped in a TCP header. The AB website may have some stuff on this.

Your easiest bet may be to go with an OPC server like RSLinx Single node or KEPWare and access the plc through that.

Look at this thread:
http://www.plctalk.net/qanda/showthread.php?t=29981

Archie has done several different projects connecting to plcs. this thread may give you some ideas.

Keith

Thanks Kamenges, I work in the education sector so there is no money to buy RSLinx etc. We are able to write our own drivers if we have details on the protocol.

I've been playing with the TuxEIP library from http://tuxplc.net and had good luck with it.

Since you're connecting to an SLC 5/05, I'd recommend downloading the DF1 manual from http://literature.rockwellautomation.com. It's publication #1770-6.5.16.

There's a file in the TuxEIP library called plc.c that has most of the details of reads and writes to the SLC 5/05. The author wrote it using block reads which work fine for integers and floats.

Reading bits works well enough, but be careful writing to bits with his library as it only lets you write the entire word, not a specific bit.

Also, his libraries don't provide for reading and writing timer and counter elements. This all comes down to the command he is using for reads and writes. 0Fx67 typed read and 0Fx68 typed write (details in the publication I mentioned above).

Using the commands 0FxA2 Protected Typed Logical Read with three address fields and 0FxAA Protected Typed Logical Write with three address fields would be much more effective for manipulating bits, and seperate elements of counters and timers.

It looks as though the author has begun working on this though because he has a subroutine to format the 'three address field data', but is making no use of it as of yet.

Anyway, it's a GPL program, so as long as your organization is comfortable with viral liscensing, then have at it.

And a quick primer on Allen Bradley 'ethernet' for the SLC 5/05.

Ethernet/IP (Ethernet/Industrial Protocol) - AB's attempt to make non-deterministic ethernet networks behave in a deterministic manner suitable for controls application. Now maintained by http://www.odva.org as an open standard.

DF1 - A serial protocol used to communicate with some AB controllers. SLC, PLC, and Micrologix controllers can accept these commands wrapped in Ethernet/IP packets via ethernet. I believe the DF1 inside Ethernet/IP combo is sometimes referred to as PCCC messaging.

Thanks Monkeyhead we will have a look at tuxplc

A quick update on progress. We have made our first sucessful read from the SLC5/05 across ethernet using the TuxEIP library from http://tuxplc.net.

Special thanks to Monkeyhead for the leads.