Hallo,
very positive news: I got a solution from terasic support.
Here is the solution message:
>Yes, we do replace the EPCS chip with Spansion Flash, and the steps
>to process the EPCS programming should be a little different.
>Before programming the EPCS via nios-2-flash-programmer, users must
>add an EPCS patch file nios-flash-override.txt into the Nios II EDS
>folder. The patch file is available in the folder Demonstation\EPCS_Patch
>of DE0-Nano System CD. It needs to copy this file to the folder
>[QuartusInstalledFolder]\nios2eds\bin (e.g.
C:\altera\11.1\nios2eds\bin), >then execute the flash-programmer.
The override file was only included within the last shipment, 3 days ago,
so I have attached this file. I also have tested it and now it is working
fine.
many thanks to terasic support ! "The service makes the difference"
Also thanks to all other people here provided me with a lot of infos.
Reinhard