Re: sd2iec ported to petSD

From: Nils Eilers <>
Date: Tue, 31 May 2011 09:29:00 +0200
Message-Id: <>
Hi Ruud,

> I had two reasons to ask if I could use a 6502:
> - I'm not familiar with the Atmels
> - I want to use the SD cards in combination with existing drives
> Then I suddenly remembered that PCs use a Intel 8042 micro-controller to
> communicate with the keyboard and that it can be addressed as an I/O
> port. My (obvious) question: can this be done with an Atmel uC as well?

Yes and no. Unlike the 8042, an AVR hasn't a hardware latch to communicate with a master CPU. In general, this can be done in software by letting the chip select signal of the slave triggering an interrupt and fetching the I/O port that's connected to the 6502 data bus. The SwinSID uses this technique, but overclocks the AVR to get the needed speed.

Though I don't like the idea of ripping existing drives to get a frankenstein flash monster, I see the advantage of getting a real compatible drive that could even run 6502 code running a real Commodore DOS. I'd like the idea more, if the hardware would be build from scratch without harming any existing drives.
Disadvantage: what about subdirectories? And data exchange isn't that easy if you store it using Commodore DOS format instead of FAT16 etc. But it could be possible to use a FAT-container with some image-files, letting the Commodore DOS only write inside the container files...


SD cards would be second choice for this kind of project since they operate at 3.3V and use a serial bus to commincate with.
But CF cards would be first choice, since they can operate at 5V, give you parallel 8 bit wide access and are very easy to connect with any 8 bit micro. A lot of homebrew projects are on the net, where people have connected them succesfully to any 8 bit CPU. You could take one or some of them as a starting point for your 6502 based CF project.

But this is a complete different project and has nothing in common with petSD.

> About using it in other computers: with 512 bytes/sector I can use it to
> replace the old MFM drives in my IBM-XT (clones) :)

There's a project in the net about replacing Apple Lisas MFM hard drives - maybe you could adapt it for an IBM-XT.
       Message was sent through the cbm-hackers mailing list
Received on 2011-05-31 08:00:03

Archive generated by hypermail 2.2.0.