ncreed@ndsuvax.UUCP (Walter Reed) (03/29/88)
I need information about how MFM data is encoded. My computer writes
directly to the disk (It's an amiga by the way) and MFM encoding has
to be done. Why do I need this info? I am writing a conversion program
for IBM format to amiga and back.
How are clock bits added? Let's say I have an entire tracks worth of
data. I will need to call a function that encodes this block for the
raw write. I also would have to be able to strip out all the clock bits
to read my data again (perhaps a verify..)
I have looked locally for information (Mags and books) but our library
here is very short on quality, up to date books. (I've flamed them
already! :-) Any info would be appreciated.
--
/* Walter Reed UUCP : uunet!ndsuvax!ncreed
Internet : ncreed%NDSUVAX.BITNET@CUNYVM.CUNY.EDU
Ph 701-235-0774 Bitnet : ncreed@ndsuvax OR NU105451@NDSUVM1
------------------- */markz@ssc.UUCP (Mark Zenier) (04/02/88)
In article <752@ndsuvax.UUCP>, ncreed@ndsuvax.UUCP (Walter Reed) writes: > I need information about how MFM data is encoded. My computer writes > directly to the disk (It's an amiga by the way) and MFM encoding has > to be done. Why do I need this info? I am writing a conversion program > for IBM format to amiga and back. > I assume you are talking about a floppy disk, in which case you need the Intel or Nec databook with the 765 floppy disk chip in it. (Actually the Western Digital 279x datasheets have more info.) Unless the Amiga has a nonstandard disk controller, you only need to worry about the format. The number of sectors, tracks ,sector size. The one catch is the inversion of the side select signal, which reverses the location of the two tracks in a cylinder on a double sided disk. (this is only a problem If you want to talk to some CPM machines like (I think) Kaypros). You shouldn't care about the the encoding since the NEC/Intel controllers and the western digital floppy controllers write the same sort of stuff. It only matters if you are trying to deal with something wierd like Apple or Commodore 64 disks. In that case your need one of the bit oriented controllers like the ones Central Data or the people that make uniform sell for the PC.
markz@ssc.UUCP (Mark Zenier) (04/02/88)
In article <1140@ssc.UUCP>, markz@ssc.UUCP (Mark Zenier) writes: > In article <752@ndsuvax.UUCP>, ncreed@ndsuvax.UUCP (Walter Reed) writes: > > I need information about how MFM data is encoded. My computer writes > > directly to the disk (It's an amiga by the way) and MFM encoding has > > to be done. Why do I need this info? I am writing a conversion program > > for IBM format to amiga and back. > I assume you are talking about a floppy disk, in which case you need > the Intel or Nec databook with the 765 floppy disk chip in it. The intel Microsystems Compenents (1984) volume II The current name for these books is the Microprocessor and Peripheral Handbook. > Unless the Amiga has a nonstandard disk controller, ... I should know better. Why does Crummadore keep doing this. It sure sells a lot of modems.
ncreed@ndsuvax.UUCP (Walter Reed) (04/05/88)
In article <1140@ssc.UUCP> markz@ssc.UUCP (Mark Zenier) writes: >In article <752@ndsuvax.UUCP>, ncreed@ndsuvax.UUCP (Walter Reed) writes: >> I need information about how MFM data is encoded. My computer writes >> directly to the disk (It's an amiga by the way) and MFM encoding has >> to be done. Why do I need this info? I am writing a conversion program >> for IBM format to amiga and back. >> > >I assume you are talking about a floppy disk, in which case you need >the Intel or Nec databook with the 765 floppy disk chip in it. >(Actually the Western Digital 279x datasheets have more info.) The data sheets I've seen don't tell you how MFM is encoded. They only tell you how big the gaps are, what sizes of sectors it can write, how to access the chip, ... >Unless the Amiga has a nonstandard disk controller, you only need to It does... >worry about the format. The number of sectors, tracks ,sector size. >You shouldn't care about the the encoding since the NEC/Intel controllers >and the western digital floppy controllers write the same sort of stuff. Yeah, well unfortunately, I do need to know about the encoding. I can get disk format from Peter Nortons Guide to the PC, but he doesn't go into quite enough detail. >It only matters if you are trying to deal with something wierd like >Apple or Commodore 64 disks. In that case your need one of the bit >oriented controllers like the ones Central Data or the people that >make uniform sell for the PC. Yep, the amiga already does this standard. It can write GCR format too, but I don't need that. The amiga routines read and write an entire track at a time, with no gaps between the sectors except between sectors 1 & 11. This allows it to get 880 K on a disk instead of 720. I can read and write a full track of BITS at a time, so I would set up a tracks worth of data in ram and just write the whole thing all at once. I guess I should have made my previous posting more concise. The amiga routines let you either deal with sectors, or bits. The amiga normally uses it's graphics coprocessor to encode and decode MFM, but I don't have access to those routines. Someone really needs to write a book on this subject, and if they have, I sure can't find it. Hell, just a magazine article would help. (I already checked for literiture locally available. The Net is my last hope!) I've gotten several replies just like the one above that basically say that the controller does it for you. That's true for most machines out there, but not the amiga. So, I still need this info! Help! :-) BTW, thanks to the people that already replied. -- Walter Reed PH: 701-235-0774 UUCP: uunet!ndsuvax!ncreed BITNET: ncreed@ndsuvax or NU105451@NDSUVM1 Internet : ncreed%NDSUVAX.BITNET@CUNYVM.CUNY.EDU "There's no point in being grown up if you can't be childish sometimes!" Dr. Who
davidsen@steinmetz.steinmetz.ge.com (William E. Davidsen Jr) (04/06/88)
There is a program for the Amiga, I think it's called DOS2DOS, which
does what you want. I assume you're doing this as an exercise...
--
bill davidsen (wedu@ge-crd.arpa)
{uunet | philabs | seismo}!steinmetz!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -mefarren@gethen.UUCP (Michael J. Farren) (04/07/88)
In article <1141@ssc.UUCP> markz@ssc.UUCP (Mark Zenier) writes: >In article <1140@ssc.UUCP>, markz@ssc.UUCP (Mark Zenier) writes: >> Unless the Amiga has a nonstandard disk controller, ... > >I should know better. Why does Crummadore keep doing this. It >sure sells a lot of modems. For reasons of economy and simplicity, Amiga (NOT Commodore, this decision was made before Commodore entered the picture at all) decided to implement their disk I/O via one of their custom LSI coprocessor chips. This allowed them to more fully integrate the disk I/O into the special multiplexed memory arrangement which allows them to do all the fancy graphics stuff they do. Since this arrangement also allows them all of the functionality of a standard floppy controller chip, I don't see why you should think there's a problem with it. The Amiga is perfectly capable of reading standard IBM-formatted 3-1/2" floppies, or writing them. What more can you ask? An IBM system can't read or write Amiga disks, and a Mac can read and write neither, so from my point of view, the Amiga system is probably superior. -- Michael J. Farren | "INVESTIGATE your point of view, don't just {ucbvax, uunet, hoptoad}! | dogmatize it! Reflect on it and re-evaluate unisoft!gethen!farren | it. You may want to change your mind someday." gethen!farren@lll-winken.llnl.gov ----- Tom Reingold, from alt.flame
markz@ssc.UUCP (Mark Zenier) (04/07/88)
In article <768@ndsuvax.UUCP>, ncreed@ndsuvax.UUCP (Walter Reed) writes: > Someone really needs to write a book on this subject, and if they have, I > sure can't find it. Hell, just a magazine article would help. (I already > checked for literiture locally available. The Net is my last hope!) > > I've gotten several replies just like the one above that basically say that > the controller does it for you. That's true for most machines out there, > but not the amiga. So, I still need this info! Help! :-) > > BTW, thanks to the people that already replied. I've already emailed this Info but I'll waste some net bandwidth on it too. In an Oem manual for a Memorex 550 8 inch drive they gave references to the IBM documents for what is now the standard MFM encoding. The titles are not exact, and these are 10 years old, but the real stuff. GA21-9190-3 Diskette General Information GA21-9190-3 Single Sided OEM information GA21-9257-1 Double Sided OEM information Try the local IBM mainframe sales office and see if they have a manual library that will sell to the general public. The seattle office used to. The above mentioned Memorex manual had everything on the formats also, like the bit sequence of the address marks, which deliberatly violate the MFM encoding rules. Find someone with an old heathkit H-11 computer with floppydisks, or try some of the other disk manufacturers, as (I think) memorex quit this business a couple of years ago. Mark Zenier
markz@ssc.UUCP (Mark Zenier) (04/07/88)
The manual number for the Diskette General info is GA21-9182-?
reeder@ut-emx.UUCP (William P. Reeder) (04/08/88)
The summary line says it all: Read a text on networking - it will
explain MFM, RLL, and all manner of interesting things (like SECDED).
I don't happen to have my old networking textbook handy or I'd tell
you the name, author, and publisher.
--
William {Wills,Card,Weekly,Virtual} Reeder reeder@emx.utexas.edu
Scholars who study dinosaurs say there were some smart dinosaurs and lots
of stupid dinosaurs. Those smart dinosaurs came along early, but in the
survival wars, please note, the stupid dinosaurs won.
DISCLAIMER: I speak only for myself, and usually only to myself.rmf@actnyc.UUCP (Robert M. Fuhrer) (04/13/88)
In article <854@gethen.UUCP> farren@gethen.UUCP (Michael J. Farren) writes: > >The Amiga is perfectly capable of reading standard IBM-formatted 3-1/2" >floppies, or writing them. What more can you ask? An IBM system can't >read or write Amiga disks, and a Mac can read and write neither, so >from my point of view, the Amiga system is probably superior. > I recall seeing a product (a software driver!) which allowed the Mac to read Lisa and Hewlett-Packard 3-1/2" disks awhile back. This was possible since the IWM (Integrated Woz Machine, the only hardware dedicated to the task) did very little of what was necessary to read and write from the floppies; most was done in software, including controlling the Mac's multiple-speed drive motors. It's really very possible that a Mac can read Amiga disks; it's just that nobody has written the software yet! -- The Foundation for Unmitigated Sillyness uunet!actnyc!rmf Department of Redundancy Department City of Kansas City, Kansas