Re: Apple II+ 15 Slots?

["Joel" <joelbuckley54.nospam.@hotmail.com>]

C800-CFFF is already used on the Apple ][+.
each slot from 1-7 has 256 bytes of memory space at Cn00-CnFF, normally used
for ROM, occasionally for i/o as well.
The space from C800-CFFF is additional memory space shared by all slots
according to a well-defined protocol. Not all cards use this space, but many
do. This includes SuperSerial Card, Unidisk interface, some 3rd party
parallel printer cards (especially if they have a hi-res screen dump in
ROM.)
Address CFFF is defined as a softswitch, which must be implemented on any
card using this address space, as clearing all cards use of that space.
Accessing the Cnxx space now activates that single card's use of the
C800-CFFE space. It uses pin 20 /IO STROBE to select it. The calling routine
should flag its use of the shared space
You should also put a byte Cn in $7F8, so if there's an interrupt routine
which might require use of the shared C800-CFFE space, on exit it can
restore the card ROM that was active when the interrupt was called.
Note that if the protocol is not followed, it would be possible to have two
(or more) cards trying to drive the bus in the C800-CFFE space at the same
time. This could damage both cards.
My memory is that the Super serial card firmware failed to follow this
protocol properly (documented in AII Tech Note Misc #3).

The //c uses the C800-CFFF ROM space which is always active.
The //e uses the C800-CFFF ROM space, too, (largely for 80-column firmware)
but has to share it with the I/O cards.
The 80 column routines have a habit of taking over this space.
If you use some printer routines which also echo to the video screen, the
//e will not always restore the I/O cards use of the shared slot ROM space.
(i.e. some software which works on the ][+ won't work on the //e because of
this)
There are fewer problems if you stay in 40-column mode.


Joel


"Bryan Parkoff" <BParkoff@satx.rr.com> wrote in message
Fa2cnSlzEqw8yA2jXTWQlg@giganews.com">news:Fa2cnSlzEqw8yA2jXTWQlg@giganews.com...
>     I have noticed that C800-CFFF are not used for Apple II+.  I plan to
> build a motherboard with 14 slots.  Each slot will be mapped to Cx00 like
> below.
>
> C100 - slot 1
> C200 - slot 2
> C300 - slot 3
> C400 - slot 4
> C500 - slot 5
> C600 - slot 6
> C700 - slot 7
> C800 - slot 8
> C900 - slot 9
> CA00 - slot 10
> CB00 - slot 11
> CC00 - slot 12
> CD00 - slot 13
> CE00 - slot 14
> CF00 - slot 15
>
>     Will 6502 CPU be able to manipulate 15 slots through 8 bit bus?  What
is
> the difference between 8080 and 6502 which 8080 support 256 I/O.  It looks
> like that 8080 and later models have more I/O than 6502 does.  What do you
> think?
>     I know that Apple //e and Apple //c will use C800-CFFF as built-in
ROM.
>
>
> --
> Yours Truly,
>
> Bryan Parkoff
> BParkoff@satx.rr.com
>
>