Rack size mismatch

[ratcliffe_ic 2]

Hi I have a 90-30 PLC which has now faulted twice with the following fault: RACK SIZE MISMATCH, both times have been since isolating the machine. The fault location says 2.0 The machine is over 10 years old and nothing has been modified in that time. Could anyone point me in the right direction on this one, my next step would be to start swapping parts machine to machine (got a few of these) Thank in advance

[Steve Bailey 118]

The configuration file is telling the CPU to expect three racks of I/O. (Rack 0 is the the one with the CPU, racks 1 and 2 are additional). When the PLC powers up, there appears to be a communications problem with Rack 2. The fault location of 2.0 indicates rack 2, slot zero. I would have expected the fault message to be "Missing rack" instead of what you're seeing, but the message still indicates a problem with the rack. Open your hardware configuration file and see what the CPU is expecting and compare that with what is actually in place. Have you downloaded the program from a PC running the programming software to the PLC recently? Perhaps because the battery was dead when power was turned off. If so, did you download hardware configuration at the same time? Make sure the interconnect cable to Rack 2 is still in place and hasn't been dislodged. Check for the presence of a terminating resistor on rack 2, especially if the cable was fabricated by the machine builder. It's also possible that the dip switches in Rack 2 have gotten changed.

[ratcliffe_ic 2]

Making sense now, I did do a download a month or so back when there was a problem following a weekend isolation, I put it down to PLC battery (didn't check the fault that time, just installed a new battery!) I didn't download the hardware configuration just the program, I'll get that downloaded and see what happens. It could be this is the 1st isolation since my download. Thanks

[ratcliffe_ic 2]

I went to do a download this morning to rectify this problem but backed out of it when my software said the firmware is not ok with my version of software. I have versapro v2.04 and the machine firmware is 5.02 and versapro says I need at least 8.21. Can you tell me the procedure to correct this and point out any risks to doing this. Thanks

[RussB 22]

You have two options. 1. Purchase an upgrade EPROM for the CPU. (You will need the CPU part number to order the correct one.) 2. Use LogicMaster Software. (You will not be able to go backwards from VP to LM, you will need to upload with LM then import the variables if needed.) No draw-backs that I know of other than the potential of third party hardware not working or needing upgrade to work with the new firmware. The up-side is that you can then upgrade to Proficy ME and retire VersaPro.

[ratcliffe_ic 2]

Thanks for the info, I suppose I could go back to my previous version of Versapro (wish I hadn't upgraded now). Would you know if you can have two versions on the same PC or am I looking at setting up a virtual machine?

[Steve Bailey 118]

If I remember correctly, VersaPro has three options regarding firmware checking. They are "prevent download", "allow download, but warn", and "allow download". It may be that your previous cersion of VP was set up to allow downloads to older PLC firmware versions without warning you about mismatch issues, and that's why you haven't seen that warning before. The 8.21 or newer firmware version "limitation" has been in place for a long time. I put the word "limitation" in quotes because as far as I know it isn't a hard restriction. It's just that there are known compatibility issues between VP and older firmware levels. If your program doesn't include any of the problem areas, you could be OK downloading from VP 2.04 to your CPU. Consider this: There are some CPU models that were discontinued before they ever got to firmware version 8.21. If you look in the Versa Pro help files for the firmware compatibility table, you will find CPU models with firmware versions earlier than 8.21 that are listed as compatible. That's because there is no version 8.21 firmware for those modules. The version listed is the highest available firmware version for that particular CPU before it got taken out of production. I was once told that the most significant issue between VP and earlier firmware versions was that certain actions taken while online with VP could cause the CPU to stop running its program. An example might be something as simple as opening the PLC fault table. If the process controlled by the PLC can withstand the PLC stopping for no apparent reason, then you may be able to use VP 2.04 without having to get a new firmware chip. This is truly a "caveat emptor" situation. I can't make a judgement as to whether you should risk downloading from VP 2.04 to the firmware level in place. All I can do is tell you that you can. The other reason I bring this up is because if you have opened the project folder under VP 2.04, you may no longer be able to open it with an older VP version. That's because unless you specified "close project without saving", when you closed the project, it was automatically saved as a version 2.04 project, which can't be opened by earlier VP versions. Edited 14 May 2012 by Steve Bailey

[ratcliffe_ic 2]

I've reinstalled an older version of versapro on my machine today, then been online to download the plc program and HW configuration.........then bottled it! I've got servo cards etc and an uneasy feeling came over me, about ending up with a non-running machine. I've got a back-up of the original program before I opened it in v2.04, so I'm OK there but I'm not sure if the HW config was uploaded when it was saved. What I did today is upload the running program and HW config as a new file, my question is, when I get the HW config fault again (which I will inevitably) could I download what I saved today and that will resolve this issue or must I download the original backup. I'm thinking that the HW config I saved today is the current state of the machine so it should resolve the problem, would this be a correct assumption?

[Steve Bailey 118]

You should compare the hardware configuration file you pulled from the PLC with the actual modules in place. Any discrepancies between what is actually in place and what the configuration file is telling the PLC CPU to expect, could be the source of the fault you reported. Be sure to look for the CPU rack and two additional I/O racks in the configuration file.