Forum Discussion

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

Bootloader Elf2Hex Woes

I'm trying to do the seemingly simple task of putting the nios code in fpga ram blocks, and at power-on, the bootloader should copy the code from on-chip memory to external sram.

In the sopc I have the cpu's reset vector pointing to on-chip memory, with the nios ide set to external sram for the prog .text. Since the code and the bootloader need to be in internal ram at power-on, I use elf2hex to convert the resulting elf file, however it is not correct... it's only 2kb, where it should be the full code + the bootloader (or around 45kb).

It works if in the nios ide points the .text to on-chip ram. Then the elf2hex file has the application code correct and can be used during synthesis to create a system that boots and executes from on-chip ram.

But how can I have the code reside in on-chip ram, and yet also have the bootloader (also in on chip ram) *COPY* the program code over to sram and execute from there?

1 Reply

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

    A carefully crafted linker script should let you link most of your code to run from the SRAM address (while being loaded into the internale memory), then just add a small piece of code at the reset vector to copy the code to SRAM.

    But I do wonder why you want to do this.

    If your code fits in internal memory then I would make it a tightly coupled instruction memory and execute from there - removing the i-cache.

    Unless you are later using the memory for something which has to be internal.