Re: A86: Flags


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Re: A86: Flags




I decided to my first real dissassembly of the rom.  If this info is
anywhere else (I'm sure it is, please point me to it):

-IY+$1E ($C403) changes between $40 and $00--bit 7--somewhere in the
keypress code.  I can't find any instruction that does either res
7,(IY+$1e) or set  7,(IY+$1e).  Do bits actually start at 0 when you are
figuring the opcode  (i.e.  $46+8*b or $C6+8*b)?
-$01ee is the start of the check for keys being pressed.  It returns at
$0220  if no key is pressed, at $0226 if one is.
-$0229 is called to read the key port.
-It uses four nop's in between it's in and out--does this mean progs should
use   4 nop's when reading the key port instead of a halt?

I'm trying to figure out where it decides where to jump to when you press a
key like 2nd+mode.  Then I could dissassemble the mode code to find all the
IY flags.



At 11:26 AM 5/27/98 -0500, you wrote:
>
>Are there flags somehwere in IY land that control the floating point number
>thing in the mode screen?  Just about everything else seems to be
>controllable, but i can't find anything about that.  I'm making a mischief
>program to teach myself about the interupt and about IY flags, it will lock
>the calc in certain modes.  If you can help me, thanx a lot.
>
>Robby Gutmann
>gutmann@planet-connect.com
>ICQ UIN: 724927      Agonostis on IRC
>
>Of course, Ankh-Morpork's citizens had always claimed that the river water
>was incredibly pure. Any water that had passed through so many kidneys,
>they reasoned, had to be very pure indeed.
>	-- (Terry Pratchett, Sourcery)
>
>


// David Phillips
// mailto:electrum@tfs.net
// AIM: electrum32


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