Date   : Fri, 11 Dec 1992 23:49:50 GMT
From   : europa.asd.contel.com!howland.reston.ans.net!wupost!waikato.ac.nz!comp.vuw.ac.nz!actrix!naos!ewen@gatech.edu (Ewen McNeill)
Subject: Re: HD controller for Z80 ???

jm59@prism.gatech.EDU (MILLS,JOHN M.) writes:

> In article <1992Dec10.115013.18326@cc.tut.fi> kent@cc.tut.fi (Kentt{l{ Marko)
>  >I could really use hard disk controller for my trusty old Z80 machine. Are
>  >any of these beasts that connect directly to Z80 or its bus still available
>  >Used is fine too ...
> Many years ago, BYTE published a two-article series showing how to build a
> simple SCSI host adapter for S-100.  The second article gave an outline of
> driver software.  The host adapter was little more than a parallel port and
> addressing logic, since the disk drive's control was quite autonomous.

Much more recently (Jan/Feb 1991) TCJ (The Computer Journal) published 
an article on how to build a very simple SCSI port.  It was just a 8255, 
and some decoding logic.  The handshaking was mostly done in software, 
except for the ACK signal which was generated by a flip-flop.  I've had 
a quick hack board made from this circuit running on my Z80 machine for 
the past 15 months without any problems.  Transfer speed is limited to 
whatever you can persuade your machine to do in software - about 45K/s 
for my 4 Mhz 1WS Amstrad.  I've been talking about adding DMA support to 
it for a while.  I might have a go at it over the Christmas break.

> How about a modern redux with IDE? Those drives are pretty good value now,
> and the interface is probably dirt-simple.  (I'm just a simple M.E., so I

This was done even more recently in TCJ (Jun/Jul 1992 I think).  It 
mostly just turned a single 8 bit port into a 16 bit port by 
multiplexing.  It apparently works quite well.  It was connected to a 
board based on a 16Mhz Z280, and I think it used the built in DMA, so 
transfer speed would have been good.  There was some software (basic) 
with it too.

> John M. Mills, SRE; Georgia Tech/GTRI/TSDL, Atlanta, GA 30332

--
Ewen McNeill, ewen@naos.actrix.gen.nz (or ewen@actrix.gen.nz)