Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

Why does NIOS write redundant stuff to SDRAM?

Hi,

I have built a system with PCIe-NIOS-SDRAM, with the program being stored in a separate onchip memory.

I am able to read and write data to SDRAM through PCIe, And also able to read and write from NIOS2, but I observe the following things;

+ When I use Printf statement in NIOS2IDE, I get the ascii code of printf written to SDRAM! This doesn't make any sense to me, I think its a debug feature, if so I would like to turn it off.

+ If I don't use printf. still a few unintended bytes are written in the code space of SDRAM. But I don't want to leave any memory locations for program, thats why I have the on chip memory.

Please let me know how to solve the above issues. I can provide more information, please let me know..

Thanks,

Ujjwal

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    12 years ago

    It sounds like your BSP linker script is not set correctly to only use the onchip memory. Check it in the BSP editor.

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    12 years ago

    Hi Ted,

    Thanks for your reply.

    Please find attached the contents of my linker script. Is it fine? Or should I change my .heap and .stack to onchip memory instead of SDRAM?

    Ujjwal
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    12 years ago

    The printf code almost certainly uses malloced memory - which is why you are seeing in in SDRAM.

    I would certainly try to get the stack in on-chip memory - and to use tightly coupled on-chip memory so you don't need to allocate resources to a data cache or large i-cache (you still need an i-cache for the boot code and JTAG debug - unless you are loading the code over PCIe).

    If you do nee careful placement of code/data in memory blocks. I'd suggest writing your own linker script from scratch - start from the documentation rather than the default script!