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| Info resources for diy floppy controller |
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| sleemanj:
The C64 floppy drive (1541) had everything built into it, and I mean everything, it had a full 6502 microprocessor and associated ram and rom inside it which handled low level controlling the drive and the high level disk operating system and protocol to talk to the attached computer. Communication to the 1541 was effectively by way of a serial connection (commodore bus) with the C64 issuing commands to the drive, the drive doing them, and returning the results. It was really more like an attached network storage if you think about it! A very very slow network. |
| helius:
--- Quote from: Dan Moos on March 23, 2019, 04:15:30 am ---Also, I'm open to everything from trying to bypass the USB interface on a modern drive, to using a vintage commodore or apple drive. The latter is probably preferable, and I assume more feasible. I think I've read old Apple 2 drives had most of the controller logic built in, whereas commodore drives didn't. I could have that backwards or wrong altogether. --- End quote --- Yes, that is quite wrong. The Commodore PET and C64 floppy drives had their own microprocessors, and the DOS or Disk Operating System ran on the drive. In the 8250 drives for the PET, the drive contains two microprocessors, twice as many as the computer! They communicate with the host using a serial "IEC" bus which is a GPIB bus narrowed down to one data bit. You could easily interface to this using a microcontroller: the host sends commands to the drive and receives file data back. The Apple II drives were the first to be totally without any internal controller, which was what made them cheaper than any offered for sale before. They were entirely controlled by software running on the computer, and they were fast. Interfacing to these drives is extremely difficult without the original Apple II hardware. |
| TheNewLab:
I don't know it this will help A youtuber called the 8-bit guy might have some stuff that might help, or just contact him https://www.youtube.com/channel/UC8uT9cgJorJPWu7ITLGo9Ww |
| DDunfield:
Back in the 80's I built a "from scratch" 6809 based portable system, hardware and software. This included a disk subsystem based on the NEC 765/Intel 8272. All of the information about it is up on my site, you can find it at: http://www.classiccmp.org/dunfield/d6809/index.htm If you look under "Documentation" -> "My minimal Hardware Notes" there is a schematic of the disk controller there (6 or 7 ICs IIRC). The source code is available "Full CUBIX package with source code". Look at OS\SAMPLE.SYS for sample drivers which include the disk interface (in 6809 assembly language). That will get you low level Initialize/Format/Read-sector/Write-sector. Most of the code that implements the higher level file system is in FILESYS.OS This was one of my earlier projects and one of my first disk controllers.. If you decide to use it and have questions, PM me I can probable help. Dave |
| helius:
This document includes some basic information about floppy drives and low-level formats. When using a FDC (floppy drive controller chip), you are limited to the capabilities of the chip, but your software doesn't need to handle such low-level details. The document concentrates on "Shugart-bus" drives that were used in PCs and other machines. Commodore and Apple used other arrangements. |
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