RSLinx DF1 frezes upon cable connect, SLC503 - no comms

Alaskan

Member
Join Date
Jul 2008
Location
Fairbanks, Alaska
Posts
10
Folks,

A SLC503 used to be connected to the Internet via a Digi One IAP. During program download to the PLC the Internet connection was severed such that the download didn't complete.

I am not the guy who used the Digi One, and I don't know a whole lot about controls, but I am the only guy on site who can do anything about the issue at this point. The plant is at a remote field camp, and I only have another 30 hours to fix this before I need to head out.

The only tool I have to fix it is an old Windows 2000 laptop that was located at the plant. It runs RSLinx Lite 2.31.00 build 10, RSLogix 500 5.20.00. The DTL32.DLL is ver 2.31.10.0, WDRV32.LIB is 2.20.118.01.

I do know that this laptop was able to connect to the PLC at some point in the past as there are previous versions of the program saved on it.

The PLC fault LED is blinking rapidly, the DH485 LED is blinking in a 3 sec interval.

The DH485 connection from the PLC leads to a DH485 Link Coupler, from there it goes to a 1761-NET-AIC module (externally powered).

I believe this was originally set up so that the PanelView 550 and a laptop can be connected to the plant simultaniously.

I can not establish communication with the PLC using the AIC driver through the NET AIC module. I have removed all drivers from RSLinx, rebooted the machine. Added the AIC driver, connected a serial cable (no name cable, one of two I found here at the plant) to the NET AIC and the PC, rebooted the PC (RSLinx is not running as a service), no error messages in the event log, no indication of problems, RSWho shows the laptop as node 0, no PLCs are present.

I switched to the other serial cable, reboot, same result.
I tried a CAT 5e cable which has DB9 converters on both ends (they are labeled 'DTE'), same result, no comms with the PLC.

I did try to powercycle the PLC, toggle the key switch any which way and back, nothing.

Now to the DF1 part. I removed all drivers from RSLinx, rebooted, added a DF1 driver with the following settings:
COM1
SLC-CH0/Micro/Panelview
19200 baud
no parity
Stop Bits 1
Station Number 00
Error Checking CRC
Full Duplex

The driver installed fine, no error messages after reboot in the event log (this is all without any cables connected to COM1). There is nothing taking a hold of COM1. I used Process Explorer ( http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx ) to verify that the only thing grabbing COM1 is RSLinx.

I found a no-name null modem cable here, as well as a null modem adapter (RadioShack). I connected the null modem cable to the RS232 on the PLC, and then as soon as I connect it to the laptop, the laptop controls freeze. After a few seconds the cooling fan of the laptop revs up. The laptop does not recover from this state even after more than 30 minutes. However, as soon as the cable is unplugged from the laptop, everything is back to normal, laptop controls work, laptop did not crash, cooling fan turns off shortly thereafter. The same happens when using the serial cable and the null modem adapter. This is also true if turing the laptop off, connecting the cable, and then turning the laptop on. It will then be stuck in the Windows 2000 loading progress bar screen, but will continue loading as soon as the cable is unplugged.

Any idea as to what I can do to restablish communication with the PLC under these circumstances?

I don't have a different computer that has a serial port. I don't have a UIC cable. I know that I would be best served with brand cables made specifically for this system, still, what I have is all I have (including what appears to be a functional Digi One IAP if that can help me somehow?). What else can I try to make this work?

Thanks in advance for your time and consideration, sorry this got somewhat long, but I felt I may as well write down all I know about the issue rather than fill in the blanks later.
 
Great information, that's a whole lot more than most first-time posters do !

There is almost certainly a problem with the grounding of the SLC; that's the only possibility I can think of for the laptop behavior when connected. It would explain some of the things the installer did with cabling.

Give me a call at the RA office in Seattle (we cover Alaska) and lets talk this thing through. (425) 746-2840. I'll be there by about 1PM PST.
 
Thanks for your quick response Okie.

Both, the null modem cable, and the null modem adapter I have do not have CD/DSR jumpered, and do not have RTS/CTS crossed.

Resetting the PLC to factory defaults didn't resolve the RSLinx lockup as soon as DF1 is active issue. I can connect the null modem cable to the PC just fine while RSLinx is running but DF1 is stopped. As soon as DF1 is running, the whole system locks up.

Realistically speaking, what are my options?
Perhaps one of the Windows Updates applied since RSLinx was installed broke the DF1 driver I am using? Is it advisable to upgrade the driver, is that even possible?

I did find the original RSLinx Lite 2.31.00 CD, is there any sense in me reinstalling RSLinx? I don't want to break what little functionality I have left. At some point the comms between this laptop and the PLC worked with the hardware I have here.

If I find a soldering iron I will make a null modem cable as described in the doc you linked, in fact, I'll just jerry rig one even if I can't solder it, will see how that goes.

The NET AIC module also has a round DIN port. I have a cable that fits in there and has an RS232 DB9 on the other end. I'll go ahead and check the docs to see whether that will be of any help.

Thanks again for the assistance, much appreciated indeed.

Edit:
Ahh, I was composing this message while Ken posted. Thanks a lot for your offer to help out Ken, will give you a ring.
 
Last edited:
Alaskan said:
The driver installed fine, no error messages after reboot in the event log (this is all without any cables connected to COM1). There is nothing taking a hold of COM1. I used Process Explorer ( http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx ) to verify that the only thing grabbing COM1 is RSLinx.
I have seen this same issue with driver conficts when using a mouse with the laptop. May not be the case, but I have seen it happen. Goodluck
 
Well then, with Ken's help we were able to resolve the issue such that the SLC is talking again and has the proper program loaded up and ready to go. Ken is awesome!

It appears the problem is with the laptop's COM port. While the COM port itself is no busted, there is some sort of underlying resource conflict happening that is gobbling up 100% of the laptops resources so that neither the keyboard, touchpad are responsive, the screen doesn't redraw, and no action can be taken unless the null modem cable is unplugged.

It was fortunate that I had a 1761-NET-ENIW and the proper 1761-CBL-PM02 cable for it. We were able to connect to the ENIW through RSLinx 2.31 using the following steps:

Communications -> Configure Drivers -> Select 'Ethernet devices' from the Available Driver Types -> Add New -> Enter the ENIW's IP address as Host Name for Station 0.

RSLinx then detected the ENIW, and the ENIW detected the SLC5/03. I had previously restored the SLC's factory settings by pulling it from the enclosure, unplugging the battery, and using a screwdriver to bridge the VBB and GND contacts on the back side (not the battery side) for 60 seconds.

Be advised that there are some graphics out there on the net which show the location of GND and VBB to be well lower on the board than the actual location (at least on my SLC 500 1747-L532 series D and E units. Be sure to look for the imprinted letters GND and VBB. On one of the SLCs those letters were very legible in yellow print (D series) while on the E series they were in small washed out white print and made it difficult to find the right location.


Once RSLinx was seeing the SLC it was trivial to add it in RSLogix, and then download the proper program to it. The program download took much longer than expected. It may be tempting to abort the upload since it may appear stalled/hung, just have patience, it works fine just takes a while.

Upon completion of the download you are prompted to accept a change in comm channels (may vary depending on what channels your program was set to use). You need to take care in considering your answer. The ENIW will continue to talk to your SLC if your SLC is set to default comm channels/settings.

If you change the channels to non-default settings while connected to the SLC via ENIW and then apply that change, communication between the SLC and the ENIW will be lost!
(Though you can of course pull the SLC, restore factory comm settings, and start over with the ENIW.)

All in all I have to say that this was a great learning experience. I didn't get much sleep last night, and I am not done yet so not much sleep this night either, but I know a whole lot more about controls than I did before I arrived here not 24 hours ago. My thanks go out to all of you who make this forum such a great resource, and of course to Ken Roach who had the patience to see this through. ;)

I'll stick around lurking from now on, I have the feeling that I didn't see the end of this system yet now that it's running again.
 
Alaskan,

I have been in your area on vacation, and I can understand your concern to get it fixed while on-site, as the next trip could require a dog sled!

With your methodical approach, the problem just had to get solved. I know Ken was a great help. Thanks for the follow-up, and keep in touch.
 

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