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Re: CFFA for IIc and IIc+?
alex.freed.007@gmail.com wrote:
On Apr 9, 5:52 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
For an Apple II, there is no advantage in SD cards at all (once
a microcontroller is required to read them), and there are numerous
conveniences.
There is no need to use a microcontroller to read/write SD cards. I
have
one on my Pseudo Disk only because it emulates a floppy. In principle
you can use bit-banging by the 6502 itself to access an SD card via
SPI protocol. A single $1 CPLD that will serialize/deserialize data
while
converting the levels 3.3 <-> 5V is all it takes for a practical
solution.
Just a matter of software drivers.
And speed. A byte-parallel interface to the 6502 driver code
makes for reasonably fast data transfers. A software bit serial
interface, particularly with handshaking, will run much slower
(and take more RAM).
Our Carte Blanche has a connector for an MMC/SD card. Somebody needs
to write a simple driver to use it as a ProDOS volume. Ideally there
should
be a way to select from several logical volumes as the cards now days
are
considerably bigger than the 32 MB max for ProDOS.
And the FPGA should provide plenty of room for a state machine to
offer a byte-parallel interface to the Apple. There is probably
good reason to buffer at least a full block of data, and maybe
a track... (no sense multiplying the number of writes, after all. ;-)
-michael
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