Disk data separator chip

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Steve Gray
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Disk data separator chip

Post by Steve Gray » Mon Apr 01, 2019 3:53 am

While researching some other vintage computers I came across mention of a data separator chip the "FDC9216B".

http://www.microtan.ukpc.net/FDC9216.PDF

I'm wondering if this would be usable with our OSI floppy controller systems? Seems like it could replace 4 or 5 TTL chips. Maybe it could be mounted in the prototyping areas usually found on some OSI boards. Anyone familiar with this chip?

I'm considering making a version of the 610 board without the RAM, and with integrated data separator. This chip could make the board a bit smaller.

Steve
C4P working, C1P working. 600D Replica working, C4P+D&N floppy not working. 505 board, 610 board, Mittendorf board, TOSIE hacker board need testing, PicoDOS disk untested.

dave
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Re: Disk data separator chip

Post by dave » Wed Apr 03, 2019 2:56 am

I think that chip could be made to work, You'd clock it around 1 MHz for a 5.25" and about 2 MHz for an 8" floppy. You may be able to get away with not having to adjust the timing of the one-shots on the controller board. However, the controller is expecting the clock pulses to have the same polarity, and this chip changes polarity at each clock edge. If the rest of the design follows the OSI design, then you could tie together the /A and B inputs on the 74LS123 to trigger on either polarity edge.

However, the reason not to use that chip is that it's pretty hard to find. A new design should always use easy to find chips. I think a PAL could do the data separation, given a 1MHz or 2 MHz clock, but the one-shot circuit is easy, requiring only two chips and no clock.

Steve Gray
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Joined: Mon Oct 06, 2008 1:54 pm
Location: Markham, Ontario, Canada
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Re: Disk data separator chip

Post by Steve Gray » Wed Apr 03, 2019 3:28 am

Dave,

Thanks for the info. I was just looking at a couple of the data separator boards I have and they seem to use 4 or 5 chips, but I admit I haven't studied the schematics to see what they do. Can you point me to the two-chip solution you'd recommend?

Steve
C4P working, C1P working. 600D Replica working, C4P+D&N floppy not working. 505 board, 610 board, Mittendorf board, TOSIE hacker board need testing, PicoDOS disk untested.

RedskullDC
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Re: Disk data separator chip

Post by RedskullDC » Wed Apr 03, 2019 11:37 am

Hi Dave,Steve et al.
dave wrote:
Wed Apr 03, 2019 2:56 am
However, the reason not to use that chip is that it's pretty hard to find.
There are plenty of pin/function compatible equivalent chips which are not toooo hard to locate.
The 9232 type chips are an upgrade on the 9216 and provide much better separation..

Couple of examples:

UM8326B:
https://www.ebay.com/itm/362408196433

WDC92C32
https://www.ebay.com/itm/163256209228

SED9420C
https://www.ebay.com/sch/i.html?_nkw=SED9420
(requires a few external components, but may be more suited as it is very configurable.

Datasheets for all three are easy to find online

Cheers,
Leslie
Superboard II - RevD, 8Kb, DABUG monitor ROM.
FPGA C1P/C2/C4. 1-8MHz, 48Kb ram, CEGMON, 16KB Hires.

dave
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Posts: 561
Joined: Tue Sep 09, 2008 5:24 am

Re: Disk data separator chip

Post by dave » Wed Apr 03, 2019 2:02 pm

Yes, the 92C32 implements a digital PLL, which is the most robust way to do the data separation. This would be the preferred method if there is significant variability in speed within one device, or between devices. In practice, the drives are pretty stable, so the advantage may not be realized.

I think these chips are great, especially for one-off designs. For new designs, I personally tend to use stuff I can order from Mouser (or Digikey, etc.). Not counting, of course, the retro CPU and peripherals that are the heart of the "retro" experience. But then, who's to say where to draw the line for a retro-based project?

Dave

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