[Coco] Glenside IDE + Multi-Pak + HDB-DOS

[RETRO Innovations]

     On September 12, 2016 at 10:30 AM "Mark J. Blair" <nf6x at nf6x.net>
     wrote:

     On Sep 11, 2016, at 23:51, RETRO Innovations <go4retro at go4retro.com>
     wrote:
     On 9/11/2016 4:48 PM, Mark J. Blair wrote:

     >> I gather that the Glenside IDE fully decodes the address bus
     rather than using the SCS signal so that it can coexist with a
     floppy controller on a Y cable.

     This I do not understand. In a Y cable situation, SCS would be no
     less valid. Can you clarify?

     If two items using SCS as their chip select were on a Y cable, then
     both would respond to any reads/writes to the $FF40 region. The same
     goes for the CTS select for their ROMs. If I'm not mistaken, a
     floppy cart responds to both SCS and CTS, while the Glenside IDE
     responds to neither.

   I don't think that is correct.  The Glenside IDE (and the SuperIDE)
   respond to the actual address lines $ff5x, but SCS is just a shortcut
   for those lines.  Essentially:

   SCS = (address[15:5] == 11111111 010);

   So, when Glenside is responding to $ff5x, SCS is also being asserted.
   Glenside just isn't looking at it.

   Mind you, you can de-asset SCS by dragging SLENB low, which is what
   SuperIDE does for any address in $ff5x (including $ff59-$ff5f), but I
   don't think Glenside does that.  You could do that to co-exist with a
   FDC, if the FDC supports SLENB.

   Jim

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     Mark J. Blair, NF6X <nf6x at nf6x.net>
     http://www.nf6x.net/
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