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Altera_Forum's avatar
Altera_Forum
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19 years ago

Program goes back to reset address

Hello all, I wrote my own boot loader based on Altera's example boot loader. The biggest differences are that my boot loader uses a defined address to load the program code and I use ldw in...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
19 years ago

Ok, I solved the problem.

I used ldw and stw to read a word from the flash memory and store it into the ram memory. But I need to use the stwio instruction to move the data to ram. This is because I need to bypass the cache. So the boot loader is working now http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/cool.gif

But there is something I don&#39;t understand. The boot loader runs a memory test, a very simple one. It stores a word on the base address of the SDRAM and load it back from that address:

stw r_mem_test_val, 0(r_ddr_sdram_base_ptr)

ldw r_mem_test_ret_val, 0(r_ddr_sdram_base_ptr)

cmpeq r_compare_resul, r_mem_test_ret_val, r_mem_test_val

But when I change these instructions to stwio and ldwio, the test fails and I don&#39;t understand why.

Could somebody give me an explanation for this?

thanks

Regards Ronald