f2xn checksum error

[Guest Ken]

hi guys. encountered checksum error when uploading my ladder diagram into fx2n. Medoc will retry for a few times quickly before flashing the message. When i try the same diagram on other plcs of same model, the diagram can be uploaded. How do i solve the problem? regards

[Guest Guest]

My first thought would be to do a 'clear memory' on the plc. Then check the paremeters on your program - make sure you are not asking for something that doesnt exist. Then try again

[Guest Ken]

I'm not very familiar with the PLC. How do I clear the memory? Thanks for the advice..

[Guest Guest]

Then we are both in an unfamiliar area. It has been a good few years since I used MEDOC (now use gx-dev) but I think it is in the 'online' section -'clear plc memory'. This will completely erase the program, data and all parameters (like a factory default setting) Whenever I have had problems with downloading - this usually works.

[Guest -Wouter-]

If you have a programming console, you can clear memory by pressing NOP -> A -> GO -> GO

[Guest Ken]

Hi guys. will search for it if it's in medoc. By the way, there's a lingering though of what if the communication port is the one having the problem?if i cleared the program but cannot transfer a new program over,what should i do? Is there such a possibility?

[Guest Guest]

If you are allowed to clear the memory then you are communicating with the plc but I know it sounds scary. If you have the original program though, you can always get out of trouble. I dont wish to scare you further but I once had a power failure while transferring and lost the lot. It taught me to always save before doing anything. If you cannot clear memory then maybe the problem is with the cable - what are you using?

[Guest Ken]

I can communicate with the plc when i monitor the ladder but there's always a retry 1, retry 2 constantly on and off. i cannot upload a new program into it because when i try to upload a new ladder, the constant retry msg keeps popping up and ended up with checksum error. I have the program saved no worries but i'm scared of not being able to upload the program after i erased it from memory. The SC-09 cable from Bjer works fine as there's no such problem with other plcs. So should i erase the program as advised?

[Guest Guest]

Ok Ken, then my next thought would be - is the medoc version you are using, up to programming the fx2n. (this model was not around when medoc was designed) I know later versions, or upgrades programmed later FX cpu's but something in the back of my mind tells me it never got as far as the FX2n. I had a similar fault to yours while monitoring an 'A' series with GPPwin. Sometimes when altering code, it had retry after retry before it was sucsessful. I also seem to recall that GPPwin did not recognise The FX2n and so I told GPPwin I was programming an FX1n and then all was ok. It might be that the CPU is faulty (seeing as you can program others of the same model) but try changing the plc type in medoc and see if it is ok then. Now I think more about it - when I went online - Gppwin used to see the FX2n as an FX0n. Just a thought but try to change the plc type in medoc to an FXon and see if communications are then ok.