[Coco] DW4 Nitros9 and floppy disk access

[Arthur Flexser]

Walter, now that I read your description of the drive's behavior with the
various slot selected, I think I understand the problem.  You want the
HDBDOS ROM to be selected (slot 3), but the floppy drive hardware (slot 4)
to also be active.  This is a situation where you want the two nybbles of
$FF7F to be set differently, with one digit selecting slot 3 and the other
slot 4.  So the value you want to poke into $FF7F is either $23 or $32--I
forget which nybble is which.

Art

On Sun, Jan 13, 2019 at 2:53 PM Arthur Flexser <flexser at fiu.edu> wrote:

> The MPI slot setting can indeed be changed with software.  Location $FF7F
> controls this.  The values are $00, $11, $22, and $33 to set the slot to 1
> to 4.  You also can set the two nybbles separately, though my memory is a
> bit hazy on what each does.  One hex digit (set to 0-3) selects which slot
> contains the ROM that is looked at.  The other selects what the SCS line
> controls, I think, so that if you are doing pokes that affect the hardware
> of a cartridge in one of the slots, like an RS232 Pak, that slot could be a
> different one than the one that the ROM is being read from if you set $FF7F
> correctly.
>
> Art
>
> On Sun, Jan 13, 2019 at 9:13 AM Walter <zambotti at iinet.net.au> wrote:
>
>>
>> However I'm not sure I like changing the MPI selector while it is on!
>>
>> Is there a way I can do this via software?
>>
>>
>>