I'm designing an electronics circuit -- in fact it's a system
expansion board which will allow a certain console to access a floppy
disk drive (FDD) -- 1.44MB standard floppy disks, the regular internal
drives you can pick up for PCs today.
I've come to realise I need a floppy drive controller IC (integrated
circuit - chip), but after quite a while I have been unable to find
one meeting this criteria:

* Relatively cheap
* Supplier who can deliver/ship to the UK
* DIP (dual-in-line package)
* Datasheets / reference manuals availible (.pdf preferred)
* Runs off +5v (most stuff does)

(and perhaps, if possible:
* Example circuits / sites on the internet)

Of course, the easier to use/interface the chip is, the better.  To
gauge the level of use, I would like to be able to control the drive
with (for example) a PIC processor (although this will not be done in
the final design) -- the address/data bus, if present, must be no more
than 8 bits.
The less REQUIRED to READ information from the disk (including support
circuitry), the better -- i.e. if it's possible to read bytes without
interrupts,DMA, that would be perfect.
I would like a list/table of any suitable chips, with as much
information as possible, and a recommendation.

---

Clarification of Question by fugit-ga on 27 Aug 2003 06:59 PDT

I will accept a list of any floppy drive controllers (with suppliers)
in DIP package, with a datasheet or reference document.

---

Clarification of Question by fugit-ga on 28 Aug 2003 07:42 PDT

Thanks to hlabadie!
It's just so hard to find information without the number "8272" :)
It's DIP, and I'm sure there are suppliers!  I even found:

http://andercheran.aiind.upv.es/~amstrad/docs/i8272/8272sp.htm

Although it would seem simple, I would like someone to explain the
connections between the 8272 chip and the floppy drive connector
(standard connector, for use with 1.44MB floppy).

Disclaimer: I am not an Electrical Engineer and cannot write a
tutorial on drive electronics and interfacing. Data are provided from
which the necessary signal and connection information can be
extracted.

First, here is a list of FDC chips with links to the sources of data
sheets.


Chipdir - Chips in the category FDC
http://www.ntua.gr/electronics/chipdir/f/fdc.htm

Among others, the Intel 8272 (and its variant 80277) and its
functional equivalent the NEC 765 will meet the specifications that
you require. Direct Memory Access (DMA) and interrupts can be ignored.
(DMA is needed only if more than one task must be run simultaneously
on the CPU, which is not a requirement here.) The data path is 8 bits
wide. They are cheap, being old designs.


Second, you have already found the data for the 8272:


Intel 8272 Floppy Disc Controller
http://andercheran.aiind.upv.es/~amstrad/docs/i8272/8272sp.htm

See also:

A-Z of CPC Chips
In this issue, as promised, we're going to...
http://www.wacci.demon.co.uk/james.htm

See also the Intel site to which a link is provided at the Chidir
site.

Third, the pinouts for the typical floppy drive will be needed. Here
are the pin assignments for the ordinary floppy's IDC.


TEAC FD-235HF 3.5" 720k/1.4M FDD
http://www.cpmspectre.pwp.blueyonder.co.uk/hardware/fd235hf.htm

Panasonic JU-257A 3.5" 720k/1.4M FDD
http://www.cpmspectre.pwp.blueyonder.co.uk/hardware/ju257a.htm

PC/AT 3.5" Floppy Disc Drive Interface
http://www.cpmspectre.pwp.blueyonder.co.uk/hardware/pcat3_5.htm

Sci.Electronics FAQ: Repair: Pinouts FAQ
http://www.repairfaq.org/REPAIR/F_Pinouts.html
http://www.repairfaq.org/REPAIR/F_Pinouts1.html#PINOUTS_049


Fourth, here are some references that will assist in the circuit
design and programming:


HOW MAGNETIC DISKS WORK
http://www.suu.edu/faculty/gardnerl/Aplus/Marcraft/RefShChp10.pdf
[This is basic information. See the section on disk drive operations
for a general layout.]


Interfacing a Floppy Disk Drive to an 80C186EX Family Processor
AP-484
APPLICATION NOTE
ftp://download.intel.com/design/intarch/applnots/27233901.pdf
[A very detailed discussion of the 80278.]

"A new addition to the Floppy Disk Controllers is the 82078, which is
functionally compatible with the 82077AA/SL (software transparent) but
includes the following additional features:
• 3.3V or 5V operation
• Small QFP package 44- or 64-pin
• New 2 Mbps data rate for tape drives
• An enhanced command set
The 82078 is not pin for pin compatible with the 82077AA/SL but
maintains the essential pins for pro- viding a PC compatible floppy
disk controller. A note in Appendix B describes how to convert
82077AA/SL designs to 82078 designs."


Fifth, suppliers in the UK can be located at:


Reg's Electronic Links
http://www.regstevens.co.uk/linkstext.htm

Choosing one likely site:

Astute Gateway electronic component product locator
http://www.astute.co.uk/

A search yields this:

Search Result Page
http://www.brokerforum.com/bfparts3?/WEBWIZARD/LIST/MemberID=astuteel

"8272     n/a  n/a       ASTUTE       AVAILABLE
                         ELECTRONICS

8272      n/a  198272    ASTUTE        AVAILABLE
                         ELECTRONICS

8272      n/a  n/a       ASTUTE       AVAILABLE"
[...]

Alternatively, the US companies JDR Microdevices and Jameco ship
worldwide. You will have to contact them by e-mail. Inquire for
availability of specific part numbers.

The 765A, for instance, can be purchased at JDR.

JDR MIcrodevices
http://www.jdr.com/interact/item.asp?itemno=gr-z80

Jameco
http://www.jameco.com


NOTE: You might need to introduce a READ/WRITE amplifier IC between
the drive and the controller.

One such chip:

Read/Write Amplifier for FDD
BH6627FS
http://www.rohm.com/products/databook/magdisk/pdf/bh6627fs.pdf


Another:

Debco Electronics Inc. -- Floppy disk read amplifier (18)
http://safe.spsp.net/cgi-bin/debco/MC3470.html


OTHER RESOURCES:
FLOPPY PINOUTS

"To test or run the floppy you will need to apply the proper logic
levels to the pins on the ribbon cable"
http://www.ohmslaw.com/switches.htm

FLOPPY CONTROLLER

Floppy disc controller and floppy disc drives
http://andercheran.aiind.upv.es/~amstrad/docs/fdc.html


Floppy Drive Forum
Re: How do I control a floppy? (Using PIC or anything!)
http://www.eio.com/public/floppdrv/0253.html


SEARCH TERMS
://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=3.5+floppy+pinouts
://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=Floppy+drive+controller+circuit
://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=integrated+circuit+retailer+UK

hlabadie-ga

---

Request for Answer Clarification by fugit-ga on 01 Sep 2003 15:41 PDT

Thanks, but as my clarification says, I really just need..

"Although it would seem simple, I would like someone to explain the
connections between the 8272 chip and the floppy drive connector
(standard connector, for use with 1.44MB floppy)."

..unfortunately, the answer provided everything but this :(

I am by no means ungreatful, but this really was what I was looking for.

---

Clarification of Answer by hlabadie-ga on 01 Sep 2003 16:19 PDT

Perhaps you overlooked the descriptions of the pinouts for the IDC on
the typical floppy. The information is explicitly shown. You merely
need to match the signals from the controller, as outlined in the data
sheet provided, with the signals indicated on the pinouts.

Intel 8272 Floppy Disc Controller 
http://andercheran.aiind.upv.es/~amstrad/docs/i8272/8272sp.htm 

TEAC FD-235HF 3.5" 720k/1.4M FDD 
http://www.cpmspectre.pwp.blueyonder.co.uk/hardware/fd235hf.htm 
   
Panasonic JU-257A 3.5" 720k/1.4M FDD 
http://www.cpmspectre.pwp.blueyonder.co.uk/hardware/ju257a.htm 
   
PC/AT 3.5" Floppy Disc Drive Interface 
http://www.cpmspectre.pwp.blueyonder.co.uk/hardware/pcat3_5.htm 
   
Sci.Electronics FAQ: Repair: Pinouts FAQ 
http://www.repairfaq.org/REPAIR/F_Pinouts.html 
http://www.repairfaq.org/REPAIR/F_Pinouts1.html#PINOUTS_049 

You should read the Intel .pdf carefully, as this gives very detailed
schematics for the interfacing of the controller both to the CPU and
the floppy.


Interfacing a Floppy Disk Drive to an 80C186EX Family Processor 
AP-484 
APPLICATION NOTE 
ftp://download.intel.com/design/intarch/applnots/27233901.pdf 
[A very detailed discussion of the 80278.]

And the use of the amplifier IC might be indicated.

hlabadie-ga

Just off the top of my head, the 8272 should work, although I would have to check.

hlabadie-ga

I apologise.
On the first couple of tries, the intel .pdf did not open correctly.
There's a circuit diagram -- which is nothing short of perfect :D

Thanks again..!

I'm glad (and relieved) that you could get the .pdf downloaded and
opened, and that the schematics meet your needs.

Good luck with your project.

Thanks for the rating.

hlabadie-ga