elements of array not accessible within loop

The classical cause is that you'll clobber your stack.

Which microcontroller, which compiler and how does the linker map look like?

You might be overwriting your stack. You can look at the linker/mapper output to see where in memory things are being placed. Often the stack is at the top of RAM and grows downward. When your data is written it is likely overwriting the top of the stack.

You guys where right. It was a problem with the stack. Now I write the critical array into heap, via calloc(). I also had to look into my startup file and set the size of the heap (standard size is 0). But even then it didnt work, so I increased the size of the stack, too. Now it runs fine.

Therefor: Great thanks!

Since this code is part of my thesis, my next task is to really understand whats all behind this and to do an accurate calculation about how much memory space is actually needed.

Sincerely, Oli

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On 2015-11-19 Oliver Krause wrote in comp.arch.embedded:

Good you found it. In embedded systems, dynamic memory allocation is often not desirable. In this case you could allocate the variable as a (module) global variable, or as a static in the function.

This avoids memory fragmentation and the size requirements can be checked compile time instead of run time (do you handle any arrors from your calloc() call?).

Downside is the memory is always "in use" and can not be re-used elsewhere (unless you write your code to explicitly do so).

You might want to consider using the Forth language. Rather than the tool allocating memory for you and having to dig out what it was that the tool did, you can allocate memory yourself and know exactly what is happening. I find it much easier to using in embedded applications than conventional tools like C.