Re: Where does the "16 SECTOR" message come from?

["Michael J. Mahon" <mjmahon@aol.com>]

sicklittlemonkey wrote:
> On Feb 20, 6:52 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
>
> > The slot ROM (256 bytes) clearly reads the disk to determine whether
> > it is a 13-sector format or a 16-sector format, but the $C800 space
> > deosn't appear to belong to the disk controller.
>
>
> In fact, it looks like it's the slot code that's bank switched via a
> store to $CX80. This should make it easier to dump. It detects the
> disk type, and then stores this code at $800:
>
> 800: LDA #$02 (#$03) ; bank number?
> 802: STA $CX80 ; select bank
> 805: LDA #$00
> 807: JMP $CX52 ($CX53) ; print "16 (13) SECTOR"? ... ;-)
>
> The values in parentheses are for 13 sector disks.

<Whack on side of head>  Thanks for reminding me that it *has*
to bank switch the slot space, since that's the only way it
can be compatible!

So the only different code is the "reset" 256 bytes, and
after it runs, the slot code will be identical to either
the 13-sector boot ROM or the 16-sector boot ROM...

-michael

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