[A83] Re: tilemap: the theory?
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[A83] Re: tilemap: the theory?
The opcode "cp" only takes one operand -- the value to compare to a.
Consider:
cp b ; check if a = b
cp 5 ; check if a = 5
cp a ; set zero flag, clear carry, etc
And i think you mean to be doing jp c or jr c, which uses the carry flag.
Carry is set if a is less than the value you just compared it to, whereas m
literally means the result has a minus sign (and the distinction _is_
important in some cases).
A revision of the code you have below:
;a = current tile
cp 2 ; 2 is the first non-passable tile value
jr c,passable
not_passable:
;... code
passable:
;... other code
In a message dated 4/16/2001 3:42:37 PM Eastern Daylight Time,
Mike3465@aol.com writes:
>
> well, you could do this:
> (a has the tile)
> cp a,2
> jp m,passable ;if it's less then 2(the 'm'(minus)) go to
> passable
> cp a,(what ever the max number for nonpassable)
> jp m,not_passable
> ;continue on if you have "special" tiles
>
> I hope that helps ^_^
>
> the jp m, bassically checks to see if it's less then the number.
----
Jonah Cohen
<ComAsYuAre@aol.com>
http://jonah.ticalc.org