PLC 5/20 communication problem

I have two old plc 5/20(1785-L20B) processors,but could not communicate them using channel 0 with my laptop although the processors run well,I can communicate with the other 5/20 processors using the same laptop and cable(1784-CP10),I also checked the SW is ok,any your guys advise me if you know why.

Have you tried autoconfigure in RsLinx? ( What happens when you do?)
Is there any thing connected to the port now or in the past ( port may not be configued for RS232-DF1.
Do you have the offline file to check configuation of port?
Also, if you can check switches for port configuration on controller. You will have to pull controller out for this ( RS232 or RS422)

Hello mickey,
Thanks for your reply,yes,I tried to communicate in RsLinx,but no success,it say check the cable and the setting....,I am sure the port is configured for RS232-DF1.I can get the offline file tomorrow,hope it could give me a clue.Thanks again.

Hi Micky,
I saw the offline program,the communication mode is User(ASCII) other than system(Point to Point),how can I upload the program from the plc 5/20?

I don't know of a way to change the port configuration without being online. I think you are going to have to connect to the DH+ port.
You will need a KTX,PKTX card for a PC ( desktop) or PCMK card for laptop
or KF2 box ( RS232 to DH+ converter). Worst case, if you have an up to date offline file you could shutdown, pull battery. This will bring controller back to its default setting. Then reload program with serial port configured as point to point.
Maybe someone can jump in here with a way to change port without the download.

EDIT:
Looks like there might be a way. Note I have never done this so
your on your own but see below for info.



http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1785-um012_-en-p.pdf

remote change enable ...

Greetings Mickey ...

the Remote Change Enable won't help - not unless he's already "enabled" it back while he was still able to communicate ... that's possible - but not likely ... maybe he has a "spare" SLC-5/04 available and can do a temporary pass-thru to come into the PLC-5/20 via the DH+ connection ... other than that, he needs to find someone with DH+ capability who can come in through the "backdoor" (or is it the "frontdoor" in this case?) and reset Channel 0 - or else pull the battery like you said and then download ... hopefully he has a current copy ... and if he's not using Channel 0 in the ASCII mode, then he needs to change that setting to "Point-to-Point" in the offline file BEFORE he does the download - or else he'll be right back where he is now ...

and the Channel 0 baud rate will default back to 2400 when the battery is pulled ... the RSLinx "Autoconfigure" feature should detect that - as long as he remembers to use it ...

PS Edit to michaelchan ...

I'm VERY short on time - but I just reread your posts and noticed that you're trying to "UPload" instead of "DOWNload" ... why? ... if you already have a copy of the program, why do you need another? ... can you tell us more about what you're actually trying to accomplish - and why? ... maybe we can come up with something that will help ...

Hello Mickey Ron Beaurort,
Thanks for your advices,I pulled out the battery of the processor,download the offline program,although I don't make certain the offline program I got is update,now everything is fine,the only thing I need to do is check the program step by step,anyway, better than I could nothing to it.Ron,I want to upload the program not download because I am not sure whether the program in the processor is update or not and I also need to modify the program,I have no time to wait Mickey mentioned KTX,PKTX card for a PC ( desktop) these hardwares arrival for urgence.Thank again Mickey,everytime you offer me a big help.By the way,do you work for AB?

Your welcome,
No, I don't work for AB (never have), I'm retired now. I was just a end user. Check the avatar, thats what I do now. I just can't seem to get this stuff (PLC stuff) out of my system.