On attempting to make the 3.5" floppy adaptor to work...

[Tristan Mumford <xtristan.xmumford@xgmail.xcom>]

Michael J. Mahon wrote:

> Tristan Mumford wrote:
>> Michael J. Mahon wrote:
>> 
>> 
>>>Michael J. Mahon wrote:
>>>
>>>>Tristan Mumford wrote:
>>>>
>>>>
>>>>>G'day.
>>>>>
>>>>>As you may or may not know I've been working on a little device to
>>>>>allow PC
>>>>>3-1/2" floppy drives to be used on a disk ][.
>>>>>
>>>>>It can now do the following:
>>>>>
>>>>>* de/Select and spin up/down the drive.
>>>>>* Detect the write-protect state of an inserted floppy.
>>>>>* Move the head around.
>>>>>
>>>>>What it can't seem to do is read and write. The basic question I want
>>>>>to ask
>>>>>is whether the apple2 has an active high or low for read and write
>>>>>pulses.
>>>>>I believe it's active high, but I'm starting to doubt myself a little.
>>>>
>>>>
>>  
>> 
>>>>Actually, it's *neither*!  The Disk ][ Controller *toggles* the state
>>>>of the write line each time that it writes a "1".  No toggle = "0".
>> 
>> 
>> So are you saying instead of the PC floppy dataline pulsing the data low
>> for a phase change, the disk ii analog card just changes state and stays
>> that way until the next phase change?

> 
> The WRITE DATA line stays whichever way it is until the next "1" (which
> is the next flux reversal).
> 
> (I find using "phase" in this context confusing, since the head stepper
> is positioned using "phase" signals.)

Because I had to "upgrade" to the bigger uC, it also ended up with a 12MHz
crystal driving it. Because it only involved very minor work I decided to
send the write signal via the uC to change it from flux reversals to
pulses.
It's probably too slow to do it though. It didn't work. Or maybe it's
reading it back via the hex inverter that didn't work.
Unless I misunderstood UTA2's section on the disk ii, the controller card
gets data from the drive in a series of 1uS, active high pulses, which
apart from the inverted state seems to be compatible with PC floppy drive
standards.

I also managed to turn an 18f452 into a nice heating element. When I did the
reshuffling I managed to short the -12v to one of its IO lines, which would
have resulted in a nice 17v potential difference inside the chip. Or is it
16v. Doesn't matter anyway. Now I have something to throw at the neighbours
cats.

I just want this silly thing to work. Using a touch of modern embedded
processing the task should be trivial.
That and I plain don't like when things don't work.

On one final note, I think I _may_ have some of those PC floppy controller
tape drives and unopened tapes in the shed. I can't remember if I sold
them. I think it would be kind of fun to get them working with a custom
driver. A //e with a 250mb (capacity probably vastly reduced for apple)
tape drive. What an odd idea. 

So, am I heading in the wrong direction?

Tristan.

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