Erik Mooney wrote:
> Actually, looking at my 6502 docs again, doesn't JMP support absolute
> indirect addressing? ie, if I store #$10 in memory location $80, and #$F6
> in location $81, the instruction JMP ($80) will jump to $F610. Trying it
> in the PC Atari debugger, the addressing mode does exist... so it should be
> possible to get single-cycle-precision delay in ROM, without
> self-modifiying code.
Heh, re-invent the wheel if you must... Anyway, this is the easy part
;) It's single-PIXEL-precision where you make the hard choices between
redundant graphics in ROM or heavy RAM usage to shift graphics around
in. In TPS I settled on a mix, where parts of the mothership exist in
three forms and other parts are recreated by shifting in RAM. It's kind
of hard to explain why--you had to be there, trying to balance exhausted
RAM, ROM and machine cycles.
Piero has also posted some very useful code samples showing how to set
up an indirect JMP as an efficient alternative to lengthy CMP-BNE
structures. Dark Mage does that in the menu branching logic. Good
stuff everyone ought to get familiar with if they want to catch up :P
--
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