Hi Tristan,
"Tristan Mumford" <xtristan.xmumford@xgmail.xcom
<mailto:xtristan.xmumford@xgmail.xcom>> wrote in message
news:459ced79$0$38159$c30e37c6@lon-reader.news.telstra.net...
> Can I ask a bit more about the 256 byte memory area?
> It's been mentioned that banking it is an option. What's the best method?
> Because I will need more than this.
As Michael mentioned in another post, if you use the "banked" (or shared)
$C800-$CFFF area, you need some extra componentry.
The circuitry required to support the banked area is fairly well covered
in the
//e reference manual : http://www.apple-iigs.info/doc/docii.htm
(Mon Dieu! C'est en Francais!)
The "Understanding the Apple2" book covers the topic to death aswell (IIRC).
The 256 byte area $CN00-$CNFF, where N is your slot number on the other
hand belongs solely to your card.
This small area is not necessarily a barrier, you could have a very
large driver
if you are happy to switch parts of it in 256bytes at a time.
Imagine that you had built the Flash card in my project and you had it
in slot#2.
If you had Bank00 of the Flash chip switched in to the $C200 space, and
executed
the following code:
C200: A9 01 LDA #$01
C202: 8D A0 C0 STA $C0A0; set high order address lines to 01 plus
set /OE low for read.
C205:......
The STA instruction has switched in Bank01 of the Flash chip.
The next instruction at $C205 will come from $000105 in the Flash chip.
You would jump back to Bank00 in a similar way by writing $00 to $C0A0.
Small overhead really, for an extra 250 bytes of driver code space.