aim-65 floppy disk control

pjmag · Post by **pjmag** » Fri May 20, 2005 10:57 pm

Hi

I was wondering if anyone had rigged up a floppy controller for an AIM-65? I have seen Dallas Shell's notes on KYM DOS variants, including one based on the 1541. I have some old 1541s sitting around and so that would look like a quick/cheap option (all I need to do is generate an EPROM with an appropriately modified DOS variant). Any other suggestions or information out there?

Cheers
Pete

GARTHWILSON · Post by **GARTHWILSON** » Fri May 20, 2005 11:58 pm

It would make sense to get a FDD going again for something like an Apple II which would have a lot of legacy code on floppies, but I don't remember ever hearing of an AIM-65 having that. How about implementing an SPI (four-wire synchronous serial) interface for a flash memory that could hold as much as a large case of floppies, all in a postage-stamp-size unit? You can get raw serial flash memories, or use something like an MMC module.

Post by **Mike Naberezny** » Sat May 21, 2005 1:17 am

Hi,

Dallas Shell's materials are the best source that I know for floppy drive information for the AIM-65.

Using the Commodore drive is a good solution for many homebuilt projects as it already has some intelligence built-in. Richard Cini and I have been working on this for some time and he has successfully extracted the serial communications routines from the VIC-20 KERNAL, cleaned them up, and successfully reimplemented them on Daryl Rictor's SBC-2 board.

We have artwork for version 2.6 of the SBC-2 board, which adds a new header. This header connects to a daughterboard with some simple electronics which in turn connectors to the CBM-IEC serial bus. We're working on pages for this project and it will be included in the mini-projects section shortly.

Regards,
Mike

Wally Daniels · Post by **Wally Daniels** » Sat May 21, 2005 9:46 pm

GARTHWILSON wrote:

How about implementing an SPI (four-wire synchronous serial) interface for a flash memory that could hold as much as a large case of floppies, all in a postage-stamp-size unit? You can get raw serial flash memories, or use something like an MMC module.

The beauty of this idea is that Read / Write Sector is more or less done for
you already ( IIRC ). This would then let you concentrate on a MS-DOS
FAT system, clusters etc. which would eventually give you access to DOS
files. I have not done this personally with Flash / MMC style memory but
I have done low level primitives for 360kb / 720kb read/write sectors.

If you decide to roll your own FDC routines, look for any PC/XT ISA FDC
card that has an NEC765 / Intel 8272 / 82077aa or National 8477 chip
on board. Then start with the lowest transfer rate ( 250kbs ) this means
very roughly that you will need to be able to handle a byte about every
13uS. As far as the actual ISA interface goes, its pretty forgiving.

-Wally

HansO · Post by **HansO** » Sun May 22, 2005 11:41 am

Mike Naberezny wrote:

.... We're working on pages for this project and it will be included in the mini-projects section shortly.

Regards,
Mike

Nice! Looking forward to these articles. Commodore floppy drives are now very cheap and widely available and have a DOS builtin. Plenty of space for files for a 6502 system. Dallas already published the details for the SYM-1 product sold in the eighties and that works fine. A bit slow, but using a parallel port modification the speed can be improved.

Hans, http://www.hansotten.com

Paul · Post by **Paul** » Mon May 23, 2005 7:33 pm

Hi,

You may want to check out http://www.6502pages.com/ that I have been working on for several months now with input from Dallas Shell. There you find software and schematics for a floppy controller that will work on a SYM, KIM, TIM, and AIM computers called FODS or File Oriented Disk System. The controller card is switch selectable for any address in memory. The software posted is for a SYM dual drive system but could be altered for any machine. The controller uses a FD1771 and 6522. The one I have still currently works with no problems at all.

For those of you with Synertek's KTM terminal there is also information and schematics for the KTM2/80 terminal which includes how to convert a 40 column to 80 with all the binaries posted.

Paul

HansO · Post by **HansO** » Tue May 24, 2005 7:04 am

Paul wrote:

Hi,

You may want to check out http://www.6502pages.com/ that I have been working on for several months now ...
Paul

Great page! Thank you!

Hans

RichCini · Post by **RichCini** » Thu May 26, 2005 2:56 am

Mike Naberezny wrote:

Using the Commodore drive is a good solution for many homebuilt projects as it already has some intelligence built-in. Richard Cini and I have been working on this for some time and he has successfully extracted the serial communications routines from the VIC-20 KERNAL, cleaned them up, and successfully reimplemented them on Daryl Rictor's SBC-2 board.

This is very true. I wanted to use this setup for a data logging application, and printers and drives are cheap.

I'd like to add that not only are the raw routines implemented, but they are done in a Commodore-compatible way, meaning that the overall API is the same as is the command sequence to open/use/close a device. It supports IEC devices 4-31, and I've successfully used both printers and disk drives with the SBC-2.

Additionally, the code contains a DOS command interpreter module which sort of looks like and operates like the disk commands in PET BASIC 4.0. Not all commands are supported, but enough are that it's convenient to use.

IIRC, the entire Serial IEC support module is just over 3k in size.

Rich

blackadder · Post by **blackadder** » Fri Apr 14, 2006 3:33 pm

dredging up a year old topic...

I worked with a guy named Don Lewis who was sort of a 1541 guru, one of his projects was called VDOS, as I recall it was a 1541 DOS that worked on various 6502 based computers.

I remember building an interface for one of our shop AIM 65's to try it out, wasn't much to it, just a connector wired to one of the 6522s on the AIM I think, might have used a TTL buffer, I don't recall for sure.

I might actually still have a copy of it in my old C64 stuff, and I'm pretty sure I have the users manual.

debounce · Post by **debounce** » Mon Apr 17, 2006 5:57 pm

Wally Daniels wrote:

GARTHWILSON wrote:

How about implementing an SPI (four-wire synchronous serial) interface for a flash memory that could hold as much as a large case of floppies, all in a postage-stamp-size unit? You can get raw serial flash memories, or use something like an MMC module.

The beauty of this idea is that Read / Write Sector is more or less done for
you already ( IIRC ). This would then let you concentrate on a MS-DOS
FAT system, clusters etc. which would eventually give you access to DOS
files. I have not done this personally with Flash / MMC style memory but
I have done low level primitives for 360kb / 720kb read/write sectors.

Among others, one enterprising chap has developed an MMC interface that connects to 4 pins on the B side of a 6522, and also a memory-mapped version. Then there is the GoMMC board which has been produced for a couple of years now and fits in a JEDEC ROM socket, and also supplies 2x8 KB of FRAM for firmware.

Quote:

If you decide to roll your own FDC routines, look for any PC/XT ISA FDC
card that has an NEC765 / Intel 8272 / 82077aa or National 8477 chip
on board. Then start with the lowest transfer rate ( 250kbs ) this means
very roughly that you will need to be able to handle a byte about every
13uS. As far as the actual ISA interface goes, its pretty forgiving.

-Wally

At 300 rpm, the nominal transfer rate for SD FM data is 64us per byte, DD MFM 32us, and HD 16us; allow +/- 2%^2 (~4%) error for varying motor speeds. At 1 MHz with no DMA, double density is doable with sacrifices, and HD is out of the question. If you need DD I can try and draw up suitable code.

Greg

EmbeddedBob · Post by **EmbeddedBob** » Mon Apr 17, 2006 7:03 pm

I've been playing with a mini DOS for my KIM for several months now using old Atari disk drives. Atari used a serial async protocol to talk to perihpherals at 19200 baud, making it very easy to hook up a simple 6850 ACIA and some software. Yes, the file management is done in the KIM as opposed to the disk drive itself, but you've got lots of flexibility, and a properly designed DOS will allow for adding higher capacity drives in the future.

Right now, the software is pretty crude. I load a 256 byte "miniboot" program into the KIM's memory, then it loads the boot sector from the drive and pulls in the rest of the system. There are subroutines to read, write sectors, format and install a bootable image on the disk. The next higher layer up is only partially written, but has routines for maintaining the used/free sector map on the disk.

A couple of other guys are getting interested in this project. If someone wants info, I'd be happy to share the simple schematic and source code. I'm open for suggestions.

Bob

orgwood · Post by **orgwood** » Mon Dec 11, 2006 6:32 am

Hi guys, I just found my ah5050 board and schematic that interfaced to the AIM65 and used the 1541 disk drive ...and interest in communicating?

DaveC

fachat · Post by **fachat** » Mon Dec 11, 2006 9:34 am

There already is some code available - I have implemented DD/HD MFM disk access using the WD1772 controller. You can find it at
http://www.6502.org/users/andre/csa/shug/index.html

Andre

debounce wrote:

At 300 rpm, the nominal transfer rate for SD FM data is 64us per byte, DD MFM 32us, and HD 16us; allow +/- 2%^2 (~4%) error for varying motor speeds. At 1 MHz with no DMA, double density is doable with sacrifices, and HD is out of the question. If you need DD I can try and draw up suitable code.

Greg

ptorric · Post by **ptorric** » Mon Feb 26, 2007 7:56 pm

btw: where can i find the theory at the base of a mfm disk controller?
thanks!

orac · Post by **orac** » Tue Feb 27, 2007 5:49 pm

Wikipedia of course!

aim-65 floppy disk control

aim-65 floppy disk control

Floppies

Re: Floppies

Re: Floppies

aim 65 1541 interface