Cyprian wrote: 19 Jul 2026 20:41
what was changed in DSP56001 asm in to run on DSP56303?
Not that much actually.
The DSP boot code is different since it has different things to set up, and the 56300 first-stage bootloader after reset expects a tiny header in the payload as opposed to the fixed 256 words the 56001 expects.
But then again this part is handled by the xbios rather than on the application level as long as you use Dsp_ExecProg
56001 dsp programs have a habit of starting at p:$40
56300 vector table is larger so a more suitable start address is p:$100, or possibly $80 if cramped on space since the last half are just user vectors.
interrupt vectors are different, as is the IO memory map, because the on-chip peripherals are not the same between 56001 and 56303.
Anything using SSI would need to be modified to use ESSI0 instead
Some of the more global registers have differences too. Interrupt enable and so on.
In terms of the actual hardware agnostic part of the code, which is the bulk of it, that runs unchanged (*)
(*) changed only because of toolchain differences.
I am using asm56k on my Mac as well as directly on Raven, so some work was done to port the dsp code which was written from a different assembler. not much, mostly just difference how macros work.
You could compile with asm56000.ttp or something else and it would be fine too, with one caveat;
asm56000.ttp tries to be helpful and wont reach the entire (bigger) IO area of 56300, spiting out error on code that is technically valid but wouldn't make sense on 56001. But for purely hardware agnostic code that doesn't touch IO you could still use it as long as you don't want any of the new 56300 instructions.
Motorolas asm56300 is windows only and wasn't ported to Atari as far as I know, so I'm sticking with asm56k for now.
