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Altera_Forum
Honored Contributor
Honored ContributorDual NIOS exception overwrite
When I load the second NIOS code, it overwrites the exception handler in the first NIOS space.
I'm using a shared ddr_sdram, but neither core's linker maps overlap. Exception addresses are 08000020 and 09000020 in the two cores. I debug the first NIOS and halt at main(). The problem comes the moment I download the second core, before anything but crt0 and alt_main run (both cores halt at main()). The overwrite data is 08000020: 00000000 00000000 FFFFFFFF FFFFFFFF 10.1 is unable to halt anywhere but main, so I wrote _start and alt_main to do exactly nothing. It seems merely downloading causes the overwrite. I confirmed the elf has nothing below 09000000 for the second code. Help??3 Replies
Altera_ForumI further confirmed that it is the download itself. I wrote the _start code for both processors to immediately loop forever. Again, nothing in the elf at that location.
I think it is a 10.1 bug.- Altera_Forum
well I don't think I'd be able to help, but if I were you I'd start looking to see what is causing the problem by:
- Would the same address range be overwritten if there was only one processor in the system? - Is the address being overwritten in fact the same as the other Nios's ISR? I'd check this by changing the Nios's base address. - Would it matter that you load the Nios that has the higher address (09X...) first, then the other one? Cheers, Kaveh - Altera_Forum
Fixed by writing my own bootloader that has one processor wait in flash until the other writes to a mailbox. Then the waiting processor continues with copying code from flash to ram.
