Need some help with MSG code in ML1000

I put in a ML1000 with MSG last week broadcasting laser info and its ran great. I found that if I pull the DH485 cable my MSG errors out and won't restart. The easy fix that I stuck in, is if it see's the error bit high, unlatch the error bit and restart the MSG. It sort of fixing the problem afterward instead of preventing. I'm sure someeone has a simple Write command code thats correctly written.

Anyway, thats not the big issue. After it was running we started noticing that one of our two print heads would stamp its commanded string twice but only every now and then. I matched up the timing of the issue today! It seems to be related to the newly connected ML1000. However, the print heads are communicating via a BAS-T module using M words over separate RS232 cables. None of the print heads logic or the laser data is anywhere near each other in the data table (I made new tables for the laser). Is that weird or what? Its as if my new logic's M words is some how barely messing with the print's M words.

You would have to post both the MicroLogix 1000 and SLC-5/0x programs as well as the BASIC program for anyone to guess what's going on.

The User Manuals, Instruction Set References, and in general all documentation recommends against manipulating any of the Control elements of the MSG instruction except the .EN (bit 15) or the .TO (bit 8). While you might be able to get a MSG instruction to reset by manually clearing the .ER bit, that is not the official mechanism and it may not always work the way you expect.

Do you need to send this data out of the MicroLogix 1000 as fast as possible, on a periodic basis, or upon the change of an event ? Each requirement will have an effect on how you write logic to trigger the MSG instruction.

I'm sending out the laser data real time but I considered making it a on demand call. I only wanted the ML1000 to relay the analog information to the main 5/03. I can set up logic to fix this easy but right now the ladder has 3 rungs of logic. The first is a MSG thats enabled all the time. The second fires off an XIC from MSG's DN [bit 13] to an OTU that unlatches the EN [bit 15]. The third is the error reset and restart handler. This setup spams as fast as it can scan. Wonder if thats causing the anomoly in the M0 files?

What a minute, are you saying the 1746-BAS-T module has its own programming? Is that why there is a DH485 port on it?

The 1746-BAS and 1746-BAS-T modules are little 80386 based System-On-Chip computers that reside in the SLC chassis. They are running a tiny little BASIC interpreter that communicates with the SLC backplane, uses the serial ports, and also has a DH485 protocol stack.

So yes, the 1746-BAS module has its own program. Usually you interact with it by connecting a terminal program (often HyperTerminal), interrupting the running program, and doing LIST and other terminal commands.

What is the host SLC for the 1746-BAS ? Is it a 5/03 that you are sending DH485 messages to from the MicroLogix 1000 ?

I would not expect the messages from the MicroLogix 1000 to possibly interact with the program logic for the 1746-BAS, but again I could not be certain without seeing your program. I trust that you are sending the MSG instructions from the MicroLogix to the SLC, not to the DH485 port of the 1746-BAS module.

The first two rungs you describe will work as long as there's never an Error (which is what happens when you unplug), and the third rung is the point of contention.

Here's an example of how I write MSG instructions when I'm sending them as fast as possible and want them to re-start after a disconnection:

I'm sending the MSG from the ML1000 to the SLC 5/03 port. I read up a bit on the BASIC card and it says the DH485 is for programming but it also says that its connected to the SLC DH485 through the backplane which is making me consider noise in the line but the data thats being transfered is solid.

Can I just plug up my 1747-PIC to the BASIC card directly or do I need to have something else? I never messed with a BASIC card before and I'm sure there is no backup for it (previous control guys just ignored basic fundementals). I'm familar with Hyperterminal. When I get hooked up to the BASIC module will it give me the information or do I have to request it? Can I do this in RUN or do I have to go to PROG?

I've confirmed that something funny is going on when the DH485 is connected. I can disconnect it and sure enough the print head stops its occasional double printing. The port affected is port 2, port 1 is peachy.

Unless you can post the *.RSS files, further speculation won't go far.

The only time I ever used the DH485 connection to the 1746-BAS module was in the early 1990s when we used a DOS software package called PBASE to connect to the module. In the Windows era, using HyperTerminal to connect to the RS-232 port of the module is the dominant method. Yes, you need to put the 1746-BAS itself into a stop mode, but you don't need to put the SLC into PROG mode to get into the BASIC module.

There are quite a few Knowledgebase documents on the 1746-BAS and 1746-BAS-T, as well as User Manuals.

RA Knowledgebase:
http://www.rockwellautomation.com/knowledgebase/

RA Literature:
http://literature.rockwellautomation.com/

Forgive me if I've incorrectly referred to the module part number. Controllers and most communication modules are Bulletin 1747, while I/O modules are Bulletin 1746. The BASIC module is Bulletin number 1746-BAS and 1746-BAS-T.