On 12/01/2011 13:48, Peter wrote:
Tony Firshman wrote:
Speaking from pretty little low level knowledge, how about abandoning
the microdrives completely (I thought you were)
So far, I could have used just one SD card interface, keeping one
microdrive.
Abandoning the microdrives completely is an option I could think about.
But the task of creating SD card signals is still not trivial. I don't
know exactly how the ZX8302 behaves internally, and which timings are
acceptable.
For example, the OS even inserts delays when just bit-banging the drive
select daisy chain, and I have no idea why this is required. Line lengths?
Noise? ZX8302 internal requirements? ... Using the ZX8302 for a completely
different purpose might require a lot of time for investigation and
experimentation.
and making your interface emulate microdrives?
Hehe, nice idea. Unfortunately it would be a pain in terms of speed, also
size would be limited by the MDV drivers I guess :)
I bet the drivers could be patched.
You could also keep one mdv if the interface was fully compatible.
It would be quite hard though switching between the two speeds. I
suppose if simultaneous access was barred, the mdv driver could be
patched on the fly.
As Malcolm suggested, a PIC could be used, and may have enough on board
storage to buffer one boot image.
Failing that it could be a bootstrap to load from the card.
Laurence Reeves
knows a *lot* about the logic.
Tony
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