Open-source floppy reader: the data separator/sync-er works!

Jules Richardson wrote: So the current must/should/nice-to-have list goes something like: MUST HAVE --------- Reading of soft-sector discs, unsynchronised, sync'd to index mark, or sync'd to MFM SYNC words READ SOFT TRACK UNSYNC, READ SOFT TRACK INDEXED, READ SOFT TRACK MFMSYNC Reading of hard-sector discs, sync'd to index marks+track mark READ HARD TRACK, READ HARD SECTOR operations Support for multiple drive interfaces: Shugart SA400/800 style (8") Tandon TM100 style (5.25") PC 3.5" Support for multiple bit rates: 125kbit/sec 250kbit/sec 720KB 3.5" 360KB 5.25" 300kbit/sec 500kbit/sec 1.44MB 3.5" 1.2MB 5.25" 1Mbit/sec 2.88MB 3.5" SHOULD HAVE ----------- Writing of soft-sector discs, unsynchronised or sync'd to index mark WRITE SOFT TRACK UNSYNC, WRITE SOFT TRACK INDEXED Writing of hard-sector discs, sync'd to index marks+track mark WRITE HARD TRACK, WRITE HARD SECTOR operations NICE TO HAVE ------------ Programmable MFM SYNC word -- 16-bit register "Stop after N index counts" mode with configurable N value Support for MFM pre-decoding Any additions or comments? Problem is, I don't have any hard-sector discs, 99% of the problems with this project are probably going to boil down to odd disc format and drive availability - all I've got is a 40/80 switchable Viglen drive for the BBC, a 1.2MB 5.25" and a couple of DS-HD 3.5" drives. Oh, and maybe an IBM 2.88MB somewhere too, but with an odd interface connector. That's my primary goal too - archiving and analysis. Building something with similar capabilities to a Trace disc duplicator would be kinda cool though. Well, as far as I can tell, the speed variation across drives is about 10% absolute max. The TEAC FD-05HF-8630 is specified to have no more than 1.5% long-term speed variation (LSV), and less than 3% instantaneous speed variation (ISV). The Samsung (SEMA) SFD321B is specced at 1.5% ISV and 1.5% LSV. Formatting systems take this variation into account anyway - IIRC the IBM format doesn't use all the (theoretically) usable 200ms zone between the index pulses. There's probably a good few tens of milliseconds gap between the end of the track and the next index pulse. My data on the IBM format is a bit sketchy though - can anyone confirm this? In any case, if what I've said is true, all you really need to do is activate /WRITE_GATE with /WR DATA high to erase the data on the track, then write the data you want on the second pass. That'll ensure that the data you've written is synchronised properly, and the controller won't be able to see any of the older data because it's all been zeroed out before the actual track was written. It might be worth taking a look at Tim Mann's CW2DMK and DMK2CW tools - they read an IBM MFM-format floppy and convert it to a DMK image, and can then write it back to disc using the Catweasel controller. It's certainly possible to make a near-exact copy of a disc. At the moment, I'm going to try and do as much as possible with the discs and drives I've got - thankfully the IBM format uses the same MFM syncword as Amiga floppies, but in a different way, so I can confirm that my sync detector and data separator works. Now I need to do the disc read/write stuff, then the host interface and software. After that? I start begging for floppies in unusual formats, and drives that can read them :) -- Phil. | (\_/) This is Bunny. Copy and paste Bunny classiccmp at philpem.me.uk | (='.'=) into your signature to help him gain http://www.philpem.me.uk/ | (")_(") world domination.