Re: Vector rotation

On Tue, 15 May 2001, Paul Kahler wrote :
> Technically ANY branch instruction can be used to select the
> secondary accumulator, but it's not used that way much if at all.
>

Do you mean *any* as in any opcode dealing with a branch or those with
that one particular bit set (bit 3 I believe)? Sorry if I seem nitpicky
here...just
curious. If I am not mistaken opcodes 0x50 to 0x57 were the branch no
select accum B and 0x58 to 0x5F were branch + select accum B.

I'm just concerned that you might be able to select the other accumulator
doing a branch based on some previous instruction. I kinda got that hint
from your post....

> Star Castle never uses the carry flag, so it's a nice game to
> start with. Flags were a big deal for me to get correct (fortunately
> I started with S.C.) If I had to do it again, I'd store the compared
> values rather than the flags. Then evaluate the flags only on a
> conditional branch - and then only the one you care about. Then again,
> we run OK on a P90, so speed isn't a big deal. The problem is that there
> are SO many instructions that affect the flags - I think anything that
> modifies/loads an accumulator.
>
> Hope that helps,
> --
> <pre>
> ___ __ _ _ _
> | \ / \ | | | || | phkahler@oakland.edu Engineer/Programmer
> | _/| || || |_| || |__ " What makes someone care so much?
> |_| |_||_| \___/ |____) for things another man can just ignore. " -S.H.
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Received on Tue May 15 12:01:00 2001