Loading of code to SRAM

[Altera_Forum]

Hello all, 

 In the system library properties I can ask for my code to run from the SRAM. I'm interested in knowing what happens behind the scenes when I compile and Run / Debug my code using the Nios IDE.  Is some loader created, prepended to my code and copies it into SRAM, jumping to it for execution ? What is going on exactly ? Can I see this loader / is this some assembly program ?  The same goes for a "production board" where the Stratix is loaded from the EPCS device. How is the code copied to SRAM ? Should I write a boot loader for that, or are there custom loaders available for this purpose ?  Thanks in advance

[Altera_Forum]

I remember that altera give a file to describle boot from flash. 

We can select auto boot from flash to sram.

[Altera_Forum]

Yes, what you describe is what happens. The build process adds a boot loader that's responsible for copying the segments to the correct memory locations and then jumping to that location. There's a boot loader specifically for the EPCS. 

 You can look at the code of the bootloader(s) in your components directory, on my machine in c:\altera\kits\nios2_51\components\altera_nios2\sdk\src\boot_loader_sources)  Andrew

[Altera_Forum]

--- Quote Start ---  originally posted by queisser@Mar 15 2006, 02:31 PM yes, what you describe is what happens. the build process adds a boot loader that&#39;s responsible for copying the segments to the correct memory locations and then jumping to that location. there&#39;s a boot loader specifically for the epcs.  you can look at the code of the bootloader(s) in your components directory, on my machine in c:\altera\kits\nios2_51\components\altera_nios2\sdk\src\boot_loader_sources)  andrew <div align='right'><{post_snapback}> (index.php?act=findpost&pid=13482)  --- quote end ---    --- Quote End ---    Thank you, I will look at that.

[Altera_Forum]

For run/debug in the IDE (not flash bootload, as previously discused), the nios2-download app is called from the IDE. nios2-download communicates to the Nios debug core (thus necessitating the presense of one in your design) via your JTAG download cable. On the Nios side of things, the processor receives a special break signal that casues it to execute code from a small monitor inside the debug core. This monitor accepts commands from your PC (nios2-download) to read/write/verify memory as required to download and debug your application.