Looking for an 8 bit FDC...

[Scott Stevens]

On Tue, 25 Oct 2005 21:21:09 +0100 (BST)
ard at p850ug1.demon.co.uk (Tony Duell) wrote:

> > 
> > 
> > OK, I'm wanting to build a board with an 8 bit CPU (probably Z80, 
> > possibly 6502) and a floppy controller IC on board with the intention of 
> > hanging it off my PC (via serial or parallel, undecided yet) and 
> > allowing me to read and write *most* formats from various 1980's 8 bit 
> > micros...
> > 
> > Intel's 8271 looks like a possibility at the moment, but I thought I'd 
> 
> I would avoid the 8271, if only becuase it's somewhat rare (the BBC micro 
> being the only common machine to use it). And there's the thing that I've 
> never seen an Intel LSI chip without a design misfeature ;-)
> 
> I'd go for one of the Western Digital ones. If you're lucky you'll find a 
> 2793 or 2797 or something like that. Everything, including the data 
> seperator, is on-chip. Setting up is easy. 
> 
> The 1770 (or 1772) or the 1773 aee other easy-to-use chips. 
> 
> Be warned that the 1771 is a bit odd. It's FM only _and_ it can write a 
> Data Marker than no other normal floppy controllers can. The problem is 
> that that data marker was used on the TRS-80 Model 1 (on the directory 
> cylinder only). If you want to copy disks from that machine, you need the 
> 1771 (to the extent that the double-density upgrades for the Model 1 
> added a 1791 or similar, and kept the 1771 alongside it).
> 
That leads into what I was going to make as a comment.  Keep the system pluggable and modular, and put several controllers on board to cover multiple needs.  Facing the micro, it's just several I/O ports per controller.


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