Re: Does anyone understand this...

[jmk3@crux3.cit.cornell.edu (Jay M. Krell)]

>I need to know what a BIT $CFFF does
 
IIGS Hardware Ref, 2nd ed., pages 185-186:
 
In addition to the small areas of ROM memory allocated to each expansion slot,
peripheral cards can use 2K at C800-CFFE...More than one can use this, but only
one at a time...A program on a card can get exclusive access to this 2K by
referring to CFFF...All peripheral cards with expansion ROM must disable their
expansion ROM upon an access to CFFF...A card that needs the 2K must first
store Cn (n is slot number) at 7F8 before referring to CFFF.
 
My summary:
 
Accessing CFFF is the "arbitration" for the 2K. Accessing it tells all cards
that someone is about to use it.
 
  --Jay, jay.krell@cornell.edu