I'll repeat - a FW downgrade. And yes, this is a link. BTW, I'd go for FW 4.6.1 as it seems FW 4.6 has some flaws.

kiril_kiryakov

Thanks for support. I download the project, the PLC goes on RUN, but the red error led is blinking. Any ideas here (with out tape the led :-)

I have recently used a FW:V4.7 for a program developed in Step7 V15.1 as if a FW:V4.3. I did not have any issues. So your problem is a surprise to me.

The official FAQ from Siemens does not mention FW:V4.7 explicitly. But there may be details that could be helpful. [LINK: How do you load a project into an S7-1200 CPU if its firmware version cannot be selected in the hardware catalog of STEP 7 (TIA Portal)?]

What my friend Jacek mentions is very valid, even if it is not mentioned in the FAQ.

There is a possible hic-up however. At some stage, a range of S7-1200 processors (some hardware build) could not downgrade; only upgrade was possible. It was a PLC with FW:V4.2 preloaded, if I recall correctly. There is a 90% chance that you will not  have an issue with following what Jacek suggests.