1747-L20C Programming Problems

Two issues regarding a problem with a 1747-L20C. It had been pulled from scrap with no firmware IC. I had an L20D and so decided to try and see if that firmware would work. When trying to copy a program configured for the L20C, RSLogix 500 says "Downloading Program - (TEST) for 1747-L20C/F ... to (DEFAULT) 1747-L20A...
This would indicate that the firmware made the processor think it was a 1747-L20A, yet it works in the L20D.

Regarding programming, I'm in a catch-22 situation. Attempting to program the 1747-L20C using a 1747-PIC and RSLogix 500, RSLinx sees the processor as a SLC500 with no problems. Memory was reset to default on the L20C, so when trying Who Active Go Online, I get a window saying "Corrupted Processor". If I try downloading to the L20C, I get the message about it being an L20A, asking if I want to procede with the download. I answer YES, and then get "Download Failed! - Communication Errors!" So, as you can see, it won't go online while only having the default program and won't accept a download while being corrupt, therefore there is no way to go online and clear faults or anything. The RSLogix 500 program definitely supports the 1747 processors as they are all listed in the selection under Controller Properties - so I don't think it is an issue requiring upgrade of software.

I did ask the AB distrib if they can supply a new firmware IC for my L20C, but have not heard back from them yet.

So, I am confused, my software is confused and my processor is confused. Please, if anyone out there is NOT confused, maybe I can get this to work - or maybe not. Any help is greatly appreciated

James C. Williams

Update: Communication problem was related to change in motherboard/RAM and it having problems running the 1747-PIC properly. I switched to using a PCMK card and driver for DH485 and was able to communicate and reprogram the L20D with no problems. Will try the other L20Cs later and report findings for future reference.

~JCW