[Coco] XPander-Coco lives!
go4retro at go4retro.com
Mon Apr 25 13:37:07 EDT 2016
On 8/31/2015 7:58 PM, Mark Marlette wrote:
> The only thing that I can think of is SLENB*. It is used to get the ghosting of certain floppy disk controllers off the bus. This is for ROM access only. The IDE hardware is IOmapped at $FF50-$FF59 by default.
Since people use this list archive for reference, I thought I'd update
At the CocoFEST, Mark and I discussed the SLENB line, and the reasons
the SuperIDE uses it (as he notes above, it's to deal with mirrored
registers on the FDC), and I did a bit of research at the show on the
SueprIDE I have.
The SuperIDE asserts SLENB line for the range $ff50-5F (assuming the
base address of the SIDE is $ff50), which is what threw me on testing (I
was hoping to put my device at $ff5c,since SIDE does not use those
Given the number of units in the marketplace, it seems more prudent for
me to select another base address.
The other issue I found is not SuperIDE specific, but is relevant to all
Glenside IDE compatible units. While I applaud the original Glenside
IDE controller designer's efforts and design in general, I guess I will
go on record disagreeing with his decision to fully decode the $ff5x
address range for the IDE interface. In effect, this greatly diminishes
the value of the MPI for IO peripherals, as it overrides the behavior of
the SCS line (which is asserted for any $ff40-5f address, but only for
the slot selected on the MPI) on the MPI, effectively forcing the IDE
controller onto the Coco Bus any time $ff50-$5f is asserted.
It's a shame, really, because this behavior essentially "halves" the IO
address space under MPI control (from $40-5f to $40-4f)
FWIW, show testing went well, and so I hope all of the bugs are squashed
and I can put the unit into production. I know there was lots of
interest at the show.
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