uninitialized mem locations problem

Hullo, I am newbie to Nios.

I have a custom board - not relevant to current question.

Nios2 6.1, no d-cache, 512byte i-cache, 16k onchip-mem with program running (mem address 0x100000-0x13FFFF), cfi-flash mem to boot from.

Me very bad in programming. http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/cool.gif

Using alt_main at the moment.

When simulating RTL-level in Modelsim, I have a problem with a memory location, stack entry, which is never written but is being read once in a while.

Eventually it ends up with giving bad address, something like

110d0:    d9c03017  ldw    r7,192(sp) // reads uninitialized value from 0x13f6c to r7
...
11b48:    3b400015  stw    r13,0(r7)  // stores to bad address

When using altsyncram model as a program memory this usually gives me 0x0 read from stack, and later some variable is stored to address 0x0.

When (for the sake of simulation) I initialize altsyncram randomly, it gives some random value. Text section is ok, since it is copied from flash.

The problem seems to dissappear if I use d-cache (not sure though, have to check more carefully), but I still would like to clarify that point.

Please explain me, what I am doing wrong with my soft.

Thanks.