520ST External Floppy only

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joska
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Re: 520ST External Floppy only

Postby joska » Tue Aug 15, 2017 3:16 pm

nico24 wrote:So finally I did get it working. Evidently all that was necessary was the correct files for the ST.


That's interesting. Sounds like the Gotek is more forgiving than real drives then :)

czietz wrote:Does anyone know why there is such a complex circuit on the PCB of some SF354?


I don't *know*, but my theory is that the single sided drive mechanism used in those particular SF354's were not proper Shugart drives, and this extra logic compensated for that.
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Re: 520ST External Floppy only

Postby ijor » Tue Aug 15, 2017 4:20 pm

joska wrote:I don't *know*, but my theory is that the single sided drive mechanism used in those particular SF354's were not proper Shugart drives, and this extra logic compensated for that.


Can you check which signals go to the 8048?

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Re: 520ST External Floppy only

Postby joska » Tue Aug 15, 2017 8:58 pm

ijor wrote:Can you check which signals go to the 8048?


I'm afraid I don't have a 354 myself. My experiences comes from replacing the drive in a friend's 354 last summer.
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Re: 520ST External Floppy only

Postby nico24 » Sat Aug 19, 2017 6:17 pm

czietz - you ARE the legend that allowed me to do that!!

I can't tell you how grateful I am that you took the time to make that page. Even if I had to translate it. It translates pretty perfectly!!

So final question - since my Atari (or external disk circuitry or both) don't allow double sided disks, is there any way I can convert a double sided disk into a single sided disk for me to read from my Gotek?

Thanks!

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Re: 520ST External Floppy only

Postby nico24 » Sat Aug 19, 2017 7:16 pm

Or maybe there is and HxC Mount with a single sided disk I can get working?

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Re: 520ST External Floppy only

Postby czietz » Sat Aug 19, 2017 7:48 pm

Thank you!

I must confess that I don't know the version of the SF354 with the additional circuit that you have. Probably the side select signal is intercepted by the microcontroller on there and it is not passed to the drive -- or in your case the Gotek. Maybe it is as easy as connecting that signal from the DIN connector to the appropriate pin on the Gotek? But I cannot say for sure. Maybe someone else has modified that variant of the SF354 for double-sided drives?

As for converting disks: perhaps it could work converting a double-sided DD disk into a single-sided one with 18 sectors per track -- but still DD! Much in the same way as I created the 1.44 MB DD(!) disk image for the Gotek that is available on my website. However, I currently have no access to my Gotek and cannot try.

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Re: 520ST External Floppy only

Postby Greenious » Sat Aug 19, 2017 10:07 pm

Side select is din pin 2 and floppy pin 32 I *think*, and yes, in theory connecting these should do it...
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Re: 520ST External Floppy only

Postby nico24 » Sat Aug 19, 2017 10:43 pm

But since I have a really old 520St - one of the first in the US I'd say, maybe I can't do double sided at all?

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Re: 520ST External Floppy only

Postby grobda » Sun Aug 20, 2017 1:12 am

AFAIK all ST's have a WD1772 FDC which can use DSDD drives. My external Cumana floppy has no extra circuitry it's just a Chinon 354 floppy and a psu. 14 pins of the drive connector are wired directly to the 14 pin DIN plug. This Doc - http://dev-docs.atariforge.org/files/Anatomy_Of_The_Atari_St.pdf - states that side 0 select comes from the YM2149F sound chip (as well as drive select). Sounds strange but it's not unusual for the sound chip to perform I/O functions - many arcade games (eg slap fight) used it for joystick inputs. Personally i've not had any problems with YM2149's but the AY-3-8910 it's pin compatible with has been a common source of problems with arcade boards i've repaired. If it were my ST I'd be testing the YM2149 and the WD1772, plus any I/O buffers if present.

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Re: 520ST External Floppy only

Postby nico24 » Sun Aug 20, 2017 1:39 am

That's very interesting Grobda. Good info.

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Re: 520ST External Floppy only

Postby nico24 » Sun Aug 20, 2017 5:54 am

I tried connecting pin 2 from the cable to pin 32 of the floppy cable. Doesn't really work as far as I can tell. I sometime get a message saying my data may be corrupted (I have converted the disk using the HxC manager). Maybe there is something else I could try....

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Re: 520ST External Floppy only

Postby czietz » Mon Aug 21, 2017 2:32 pm

Did you check if the side select signal (pin 32) is connected to something else? Then you may have to cut that trace. However -- since I have no first hand experience -- I'm still hoping someone who actually modified that version of the SF354 will come forward.


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