[Coco] FDC Emulation ( was Re: A semi-real CoCo topic)

[Bob Devries]

Michael R. Furman writes:
> My idea is to have enough hardware in the Coco's cartridge slot to sit
> and listen to the floppy controller ports and send the commands over a
> wire to a PC (USB?), where it emulates the control and data registers of
> the WD FDC and just reads and writes blocks directly out of image
> files.  

Hehe, this sounds suspiciously like Cloud9's DriveWire.

--
Regards, Bob Devries, Dalby, Queensland, Australia

Isaiah 50:4 The sovereign Lord has given me
the capacity to be his spokesman,
so that I know how to help the weary.

website: http://www.home.gil.com.au/~bdevasl
my blog: http://bdevries.invigorated.org/

----- Original Message ----- 
From: "Michael R. Furman" <n6il at ocs.net>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Thursday, July 26, 2007 2:05 PM
Subject: [Coco] FDC Emulation ( was Re: A semi-real CoCo topic)


> With the news of the nearly complete coco3 fpga this idea may be
> obsolete before even starting-
> 
> I was dreaming up a better way to hook your Coco up to a computer with a
> library of disk image files than exists today (I still use sneaker-net).
>>From what I can tell, the existing solutions either use the serial port
> or seem expensive (I'm cheap) or complicated (some thing I saw at a
> Vintage Computer Festival a few years ago required a card and an adapter
> box thingie).  Please let me know if you disagree with this statement:
> tell me why, and which existing solution works well for you.
> 
> My idea is to have enough hardware in the Coco's cartridge slot to sit
> and listen to the floppy controller ports and send the commands over a
> wire to a PC (USB?), where it emulates the control and data registers of
> the WD FDC and just reads and writes blocks directly out of image
> files.  
> 
> Some notes on this idea:
> 
> 1) I have only so far done a surface read of the WDC FDC data sheets
> 
> 2) I have only so far done a surface read of DECB unravelled
> 
> 3) I'm a software guy, and hence the hardware part is simplistic-minded.
> The software part seems like an implementation of a finite state machine
> would do the trick. Receive a command, move to state, perform action,
> move to state, send a reply, move to state, etc.  The details of the
> required FSM structure can be easily constructed from any flowcharts or
> detailed descriptions of FDC command operations in the data sheet.  This
> will be a pretty close approximation of what's happening in the hardware
> since most digital logic design works on a FSM paradigm anyway.
> 
> 4) As far as I can tell from my surface reading so far, doing things
> this way will help alleviate timing and compatibility concerns  (If for
> example the floppy drive end were emulated, this is asking for timing
> troubles).  I'm imagining that the Coco will read/write bytes to/from
> the data buffer at its leasure and that the other end will be able to
> service the data buffer at least 5x faster (floppy drives achieve a
> throughput of around 150-300kbps and usb1.1 is around 1200kbps)
> 
> Is this crazy?  Even if it is crazy, anyone want to help?  This could
> also be a good idea starter for the FPGA implementation...
> 
> --Mikey
> 
> On Thu, 2007-07-26 at 12:46 +1000, Bob Devries wrote:
>> Would it be possible to use part of the FPGA to act like a disk drive 
>> interface, possible IDE or even floppy?
>> It sounds like you could just about have a coco3 in a cigar box :)
>> 
>> --
>> Regards, Bob Devries, Dalby, Queensland, Australia
>> 
> 
> 
> 
> 
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