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Re: How much of a ][ is needed to twitch?
Michael J. Mahon wrote:
> Tristan Mumford wrote:
- on the location of RAM in an apple][ -
>> That sounds like a nice test to me. It will be the first thing I try.
>
> Aaack! I got it wrong *again*!
>
> As Jorge points out, Row C (on the PC board edge) is the low 16KB,
> row D is the middle, and Row E is the high ($8000..$BFFF) row.
>
> It has *definitely* been too long since I played with my ][+. ;-)
Tsk tsk. I'll bet its in a corner sulking.
-snip-
>> Then there are a few other tricks that can be pulled too. One good
>> example is somewhere on microchip.com I think its in a pdf called tips 'n
>> tricks or something like that. One example is independently controlling a
>> lot of leds using a few IO pins. They take advantage of H, L, Z states to
>> swap input and output, or disable.
>
> Electronic Design News recently published a general method like
> this to control N*(N-1) LEDs from N port lines:
>
> http://www.edn.com/contents/images/6406730.pdf
>
>> Then there are other tricks like a single wire numeric pad sensor using
>> capacitance etc... I've wandered badly here.
>
> I've seen this most often with resistors, to time an RC delay
> or as input to an ADC.
The tips and tricks file on the microchip site is worth a look. I'll have to
dig it up off a backup cd to find out its name.
I'll give that document ^ a look too. First I'm going to finish reading the
disk ii section of UTA2 though.
>
>>>I applaud your restraint. ;-)
>>>
>>>
>>>>I tested my "secret" project today. It didn't work. When I start seeing
>>>>results / make it look less pathetic / pose less danger to people's
>>>>precious hardware I'll reveal more. Or I guess if I'm asked nicely.
>>>
>>>Pretty please...with chocolate fudge and sprinkles on top... ;-)
>>
>>
>> Okay :)
>> It's a drop-in (according to the apple][) 160 track single sided 3-1/2"
>> floppy drive.
>> It will have other features later like a side A/B mode using a switch.
>> and support different density drives.
>
> Sounds like fun!
>
> Maybe the drive select line could be used to do the side select?
>
One of my many ideas too. It would be rather nice to have two "disks" in the
one unit.
I discovered I was limited by a crippling lack of 20 pin ribbon cable
though. The one I'm using I pulled from a very convincing clone Disk ][.
The only indications that it isn't the real deal is lack of labels and no
apple branding on the circuit board. nice quality though. It's made of what
seems to be 1mm plate steel.
>> My test was without my magic logic too. It was just a straight-through
>> wiring of the matching control signals and a power adaptor.
>> All it did was spin up on powerup and just keep spinning, even after
>> dropping back to applesoft which should have stopped it. What really
>> surprised me is the drive kept going in both A and B configuration
>> (before and after twist). Tested with two different drives too.
>> I only wired drive A enable, not B. Although I should have done B and not
>> A. Oh well. Least of my errors.
>>
>> I've already written the microcontroller control code mostly. I still
>> have to settle on IO pins and figure out resistances for the voltage
>> dividers for the stepper reading.
>
> What, exactly, is that used for (the Disk ][ controller steps
> open-loop)?
I made a mistake. Somehow I got the idea that the lines in the cable were
providing driving current and voltage to the stepper phases, not just the
logic.
>
> ..or maybe you mean picking pullups/downs for the phase signals
> (which are 'LS259 outputs)?
This I may still have to do given the unexpected operation of the floppy
drive. I'm going to check for any shorts and incorrect wiring before trying
again. As far as I'm concerned it should have shown some signs of sanity.
Ie disabling when resetting to basic.
I'm fairly sure the logic of the controller is compatible with the floppy
drive and shouldn't need anything like pullups. Can someone (dis)agree with
me on this please?
-snip-
>>>Sather describes an elegant (if that can be said of a jumper-based
>>>approach) method for taking over RAM space, but it is not a native
>>>capability.
>>
>>
>> Interesting, but probably would not be worth the effort. Would it?
>
> It might be worth it as an experiment. If the control were decoded
> properly, it could simulate (part of) //e memory banking, which might
> work with some //e software. ;-)
>
That's what a IIe is for. But the hack value of trying that does appeal to
me. Especially if it would work as a prodos ramdrive... or NVRAMdrive. I'm
still looking for the perfect use for the 64k NVRAMs I have.
Tristan.
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