SLC5/03 to Laptop Comm problems

[jraef]

Forgive me brothers, for I have sinned...

Not really, but I am about to. I have a project with a SLC5/03 processor, W98 laptop with a serial port (so rare now I dare not give it up) and RSLogix 500. When I first power up my SLC system AND do a fresh boot on the laptop, I can download my program into the SLC. Then I go on line and everything is fine. After being on line I can view my program (troubleshooting it right now), but as soon as I go into my Alarm subroutine for any reason, I loose comms! Once lost, I can't re-establish it. I keep getting the timeout on the RSLogix program essentially telling me it can't find the processor at that node / address. At first the PLC processor kept locking up on hardware watchdog timeouts, but I think I figured that out because I had forces in the test program, and when it loses comms when forces are enabled, the SLC CPU must go into lockdown as a fail-safe condition. I removed all the forces, killed power everywhere, was able to reload the program, and it worked. But again, as soon as I went into the Alarm subroutine, I lost comms again! I have a backup processor card and stabbed it in, does the same thing. I tested the RS232 cable, no apparent problems. And like I said, I can load the new program ONCE when everything is fresh, but sooner or later I lose comms, and it seems to only happen when I enter that Alarm subroutine. Arrrrrgghhh!

Any ideas?

JRaef.com
Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[dpc]

Is the RXLogix software you are using actually supported on Win98?

BTW, the PCMCIA card serial ports are supposed to work well. I know relay techs who use them on a daily basis for communicating with protective relays for testing.

We've used USB/serial converter with mixed success. Mainly depends on whether or not your application software allows something other than COM1 or COM2.

Other than that, I'm afraid I'm no help.

 

[ScottyUK]

The SLC5/03 is our site standard processor, but we tend to use the DH-485 port for programming. We found that NT4 proved much more stable with RSLogix 500 than Win95 or Win98 ever did on our old Compaq Armada M300. This seems to conflict with results some other people have reported, which just goes to prove that A-B's software is flakey.

We were using the awful 1747-PIC converter until recently. Do not buy this converter: it will drive you crazy with its flakey behaviour and seemingly random failures to work properly! The SLC5/03 DH485 ports have behaved well with the new USB-DH-485 interface, p/n 1747-UIC, plus that item is quite reasonably priced (~ £100) compared to the 1784-PCMK (~ £1000). We have not seen any adverse effects on any of our systems while using the DH-485 / 1747-UIC combination under XP SP2 on a laptop of more recent vintage.

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Sometimes I only open my mouth to swap feet...

 

[itsmoked]

jraef; Repent brother!!

Actually I no nuthin about that particular piece of hardware but offer only a suggestion that once got me the same way. Does "alarm mode" actually trigger a physical electromagnetic device? Could be inductively hammering itself. (I've seen this)

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

Thanks for all the suggestions. After talking to my customer last night I discovered that they had been using the laptop and that software prior to hiring me and had no comm problems. So obviously something had changed. Some of the Alarm sub routine was existing, I just expanded it. I couldn't see any reason for that yo have made a difference.

When I got in today, I just stood back and observed the site looking for some simple thing I was missing. Bingo!
When they had been working previously, the system was in it's infancy and they were working off of extension cords. Now the system was hooked up to main 3 phase power, except for one not-to-minor detail. The system needed 480V and they only have 208, so they used a transformer to step up. What I observed was, only 3 conductors coming out of the transformer into the MCC bus! They didn't think ground was very important just for testing, so they didn't run a ground cable!

I made up a ground conductor today, all my problems went away. As far as I can speculate, the Alarm subroutine involved a lot of traffic back and forth to the laptop while I was monitoring and that probably created ground currents or static on the comm cable, which made errors on the CPU, laptop or both. Nice clean ground path; no more errors! I'll need to file that one away under my "Check this first" folder.

Thanks for all the suggestions anyway. I learned from them as well.

JRaef.com
Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[LogicControls]

I will try a basic virus scan .

 

[ScottyUK]

That's lovely for you, I'm sure. Does it have any relevance to anything in this thread?


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Sometimes I only open my mouth to swap feet...