Siemens S7-400 Downloading Issues While Test Mode On


Thread Starter


Hello guys,

I would like to add here a discussion about S7-400 software. I was at customer today and experienced something really weird.

I was trying to download a change I made into a block, and I could not download to the PLC. It was complaining about the test/debug mode on. So as I know some other programmers might be playing with that PLC early my shift the only way I could get the download going through was by rebooting the PC.

Does anyone out there has any information about issues performing downloads and what possibly causes not allowing user to download?


Gabriele Corrieri

Hello Placido

Some question about:

-is that the first download to the cpu or today you have modified that block (or something else) before?

-are you connected to the cpu with ethernet, in other words: is the cpu PN or are you connected thru CP443?

the last question is about pn drivers on your pc: randomly they crashes or might not full functioning, if appear again kill any process that the name start with "pnio" and/or close and reopen step7

I've assumed that you're running step 7 5.5 with the latest upgrades, if you're running Tia Portal is another question that I have not encountered yet.

Hope this helps


david mertens

Hi Placido,

You can not download while someone (you or someone else) has any other online connection to the PLC (e.g diagnostics or online blocks open). Rebooting the PC will not solve this (unless it was the PC that had the online connection open), it is a feature.

Kind regards,