Using a PIC as a floppy disk controller

That reminds me. I've been using an IDE-to-USB adapter for some time now as a simple system backup solution (something like this, found from pricewatch.com):

Does this type of adapter have a microcontroller built-in?

Michael

Probably not as such, although there's a LOT of digital logic in a design like that (I guarantee it'd be a custom IC), and some or it is almost certainly something pretty close to a CPU (more like a microcode sequencer for, e.g., fancy state machines) if not an actual CPU core.

There is a compilable VHDL description of the 1770 chip.

This seems the best way to go, given that it works and has source code and the PIC is nowhere near fast enough.

Actually, I think SD cards would be better, since it takes very little hardware and stores far more than floppies. My laptop PC doesn't even have a floppy disk or RS232 anymore, just SD card and USB.

I am almost interested. How much did they store per unit of media?

Cool, maybe you could post a table of contents?

In 1999 I scanned many pages of the WD-1973 data sheets and app note.

Over in alt.binaries.schematics.electronic I posted a zip file of the app note for the WD-1793.

Its a poor scan, but those who are interested in why it is not easy to decode the MFM serial data from a floppy disk can read about that in the .pdf file.

Good Luck

donald

See...

for how I was doing it (1983) for a portable device with lousy motor speed control.

...Jim Thompson

Jim,

Thanks for this link.

I misplaced this file and have been looking for it when this topic came up.

Not that I'll ever use it, but its a good reference.

donald

I designed that in '83, but had a hell of a time getting the digital guys at GenRad to use it... until I invited the big boss down to my lab to watch me swing a PSP(*) around and over my head while the circuit kept right on reading.

(*) PSP = Portable Service Processor... a large-brief-case-sized pin-driver tester.

...Jim Thompson

Not on a single sided single density disk. It was 170K. 664 256 byte sectors for data, 18 sectors for the directory with a max 144 files, plus a sector for the FAT. That is a total of 683 sectors * 256 or 174848 bytes, or 170.75 KB per disk. The double sided 1571 had double the capacity, and could read IBM formatted disks with the built in WD FDC with software to configure the drive. It was able to be programmed for other formats, as well.

It might be fun to made a compact flash to Commodore adapter for the C64 and C128 collectors out there. 2 GB of removable storage for a C64 would have been amazing 20 years ago.

It's been done -- see the Commodore One page at c64upgra.de/c-one . Although its development is now done worldwide, its roots began here in Oregon -- Jeri Ellsworth did the bulk of the original work; I contributed a sample uber-simple SDRAM memory controller for the thing (dunno if it was ever actually used) and helped a little with the floppy decoding.

---Joel

Is that for her new computer, or for the orginal C64?

hurdles.

Err- for 3.5" and 5.25" drives, and even old PC single-sided 5.25" drives, any PC motherboard will work OK. But, I have 8" floppies from a DEC system, and AMD multibus computers, and Apple disks, and Commodore, and those AREN'T compatible.

Apple's Macintosh floppies, for instance, used zone bit recording and had multiple-speed motors. Ya can't write those easily (and reading them on a PC is a difficult task). The issue isn't the data, which can be read from the head(s) fast enough with a PIC; it's with things like the (required) speed control logic, feedback controls for tracking, and suchlike. Minor matters like decoding the track info are something anyone's computer can handle in software, but the servo signals that kept the drive on-track are not generic, lots of different drives need their controllers to handle these details.

Hi Michael,

The new computer, although I suppose there's nothing special that would prevent its adaptation to the original C-64 (although I don't know how the card reader hardware is accessed... probably memory mapped, I suppose...)

I'd be willing to sacrifice a 1581 3.5" drive to build one if I can design the interface. Use a 3.5" CF adapter to fit in the drive bay, and replace the existing PC board with the new logic.

How about a bank switched version for the cartridge slot? Just think, an old 256 MB module would hold over 8000 games or other programs. Just select the one you want from a menu, and reboot. ;-)