🚀 go-pugleaf

"Franc Zabkar" <fzabkar@iinternode.on.net> wrote in message 
news:lai8q49t07jt8br6iqork0qdoof2u0fq25@4ax.com...
> On Tue, 24 Feb 2009 17:43:49 +1100, "gcd"
> <gcdmelbnospam@deletemelbnospam.iimetro.com.au> put finger to keyboard
> and composed:
>
>>I've had some success using a standard pc drive. Had to use DS0 rather 
>>than
>>DS1 (expected)  and needed to ensure the drive was using disk change on 
>>pin
>>34. The only thing that is still a little peculiar is the density select 
>>and
>>whether it's an input/output or both. Using a standard PC drive I need to
>>use a HD disk but cover over the HD hole and that seems to work reliably. 
>>On
>>the original drive I would use HD without covering up the hole. The only
>>issues I end up with is that the drive light is always 1/2 on when not in
>>use.
>>
>>I'll keep looking for FD-235GF data and playing around. i'ts almost sorted
>>now
>>
>>Thanks
>>Greg
>
> This URL suggests that pin 2 is an input to the drive:
> http://pinouts.ru/Storage/InternalDisk_pinout.shtml
>
> I suggest you look at the datasheet for an old multi-IO chip such as
> were used on 486 and Pentium motherboards, before the functions were
> incorporated into the chipset.
>
> For example, here is the datasheet for a Winbond W83757F:
> http://www.datasheetarchive.com/datasheets/Datasheet-022/DSA00379504.pdf
>
> Amongst the FDC pins is RWC, Reduced Write Current. "This signal can
> be used on two-speed disk drives to select the transfer rate."
>
> Logic 0 = 250 Kb/s
> Logic 1 = 500 Kb/s
>
> It is described as an "open-drain output pin with 24 mA sink
> capability".
>
> I've seen this pin used in 2-speed 5.25" drives, but not in 3.5"
> drives. It could be that the HD hole in the diskette tells the [PC]
> drive what write current to use, but the drive does not report the
> diskette type to the controller.
>
> Does your Advantest network analyser write 1.44MB or 720KB of data to
> the diskettes? It would seem odd if the drive were writing to the
> diskette as if it were a 720KB lo-den type while the controller were
> transferring data at a hi-den (500 Kb/s) rate.
>
> Could it be that your current setup is operating at a 250Kb/s data
> rate, and that your diskette's capacity is being reduced to 720KB?
> Could it be that the original FDD uses the "RWC" pin as an output
> rather than an input, and that it communicates the diskette type to
> the analyser, in which case the analyser could automatically adjust
> the data rate to suit??? In the latter case, if the analyser doesn't
> get any feedback from the drive, perhaps it defaults to a lo-den data
> rate. You might like to experiment with a pull-down or pullup resistor
> on this pin.
>
> - Franc Zabkar
> -- 
> Please remove one 'i' from my address when replying by email.


Hi Franc,
yes - pin 2 determines the density of the drive which is usally related to 
the speed of the drive. Some fdc chips expect this to be sent to the dhip 
from the drive, some expect to send it out to the drive and others are 
bi-directional. Just depends on the age of the drive and the controller,  as 
things changed from shugart to pc format interface.

This is why I'd like to get the jumper info - it would tell all.

I've had a bit of play with pull ups with no luck but I'll persist :)

Thanks for the links and suggestions, mind you, if all I end up with is a 
light 1/2 on I can live with that - just need to ensure the configuration i 
end up with is reliable in terms of data storage


Greg