On Tue, 12 Sep 2006 01:42:22 -0700, "Michael J. Mahon"
<mjmahon@aol.com> wrote:
The idea here was to use the same drive on the ][ and /// line using
the proper host cable, the A2 being 19 pin, the /// being 25 pin. The
FileWare floppy (Twiggy) was slated for a 25 pin external version for
the /// as well.
.....
There are two wires from the controller: /ENBL1 and /ENBL2, which are
drive select 1 and drive select 2.
On the 20-pin card, only the corresponding signal is connected to the
pin for the drive enable line.
On the 19-pin card, both enable lines are connected, one to the "drive
enable" line for the (first) disk, and one to a spare line that is
crossed over to the "drive enable" line output on the daisy-chain
connector of the first drive, to select the second drive in the chain.
This is exactly the same approach used with the Apple III, but with
three external disk select lines. Apple III drives "shifted" the
select lines "down by one" on their daisy-chain output connectors,
so that subsequent drives would be selected by consecutive higher
drive select lines.
I am referring to the question about Apple III with Apple Drive ][
because I like to know if anyone has carried out a "converter" to
utilize this drive for external use with Apple III. I think Apple III
and Apple II controller send out very similar signals, but they have
26pin and 20pin cables ...