8-bit IDE

From: Richard Erlacher <edick_at_idcomm.com>
Date: Mon Apr 17 00:43:41 2000

The reason for using CPLD's rather than the TTL MSI parts is that the CPLD's
drive harder and better (symmetrical outputs) and don't require changing the
wiring when the logic has to be fiddled with. The board, of course, has the
0.10" wirewrap matrix, so a package that will fit on that will be a
requirement. I figure a SMALL CPLD, e.g. EP 1800 will fill the bill.
However, I hope to get by using the 8-bit channel if that's for real. There
are some small (68-pin) CPLD's that cost about what the TTL would cost, i.e.
about $9, including the socket. SO packages are out of the question since
I'm not making a new PCB, but rather using unpopulated boards that already
exist. At present it looks like I can use the resident buffers and logic to
decode space for a SCSI (NCR53C80) a WD100x-series board, and this 8-bit IDE
would get all its signals from the same place as the WD100x channel, since
they're very similar. All this for swapping an 'LS682 comparator with a

----- Original Message -----
From: John Wilson <wilson_at_dbit.dbit.com>
To: <classiccmp_at_classiccmp.org>
Sent: Sunday, April 16, 2000 7:12 PM
Subject: Re: 8-bit IDE

> On Sun, Apr 16, 2000 at 05:04:18PM -0600, Richard Erlacher wrote:
> > If I were
> > willing to add any components at all, which would be the case if I had
> > use the 16-bit interface I'd certainly not fiddle with the TTL MSI. I'd
> > inclined to use a CPLD since they can drive the cable.
> Well you do what you gotta do. IMHO this job is just too easy to waste a
> CPLD on it, I felt a bit funny about even using a PAL for the decode but
> I was just building one board so I would have spent more time wiring than
> I spent burning PALs. Anyway the loose parts will cost less than the CPLD
> and they're less likely to get discontinued in a year. If you're tight
> space you can use the SOIC versions...
> John Wilson
> D Bit
Received on Mon Apr 17 2000 - 00:43:41 BST

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