21 Aug
2009
21 Aug
'09
3:42 p.m.
Hi Peter,
Why should it? I presume the CPU starts at _start, so it will "b reset", i.e. branch (jump) to "reset" and be happy. Its only if the CPU jumps to one the reserved vectors that it will loop. And well, as they are reserved, this is a legal thing to do, no? As the purple port works, I'm pretty sure they do not usually get jumped to there ;)I knew I must be missing something, I didn't see that the reset definition comes straight under all the other vector calls, so _start just runs through all the vectors if for some reason reset returns (twice) and would get trapped because of RVECENT(romReserved,2).
It seems to me that you may still be missing the point that a "b reset" is an unconditional jump, not a call, i.e. we will never return to the next instruction. A call would be a "bal reset", i.e. "branch and link" which puts the address of the next instruction into the $ra register. One would return with "jr $ra".
As I'm not really into MIPS, please don't ask me why MIPS has branch *and* jump mnemonics - I don't see how they designate different concepts.
Cheers Detlev
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