Gee! I thought I had trimmed the excess from the message I sent. I get a
couple of hundred emails every day, including this mailing list, and,
frankly, I need all the help I can get in associating the current level
message with the context. Message subjects certainly don't help much since
the fractional portions that warrant my interest aren't always entirely
central to the initial thread title.
The reason I like the '646 and friends is because it essentially provides
the register that is needed to hold the high data on a read and the buffer
to steer the high data on a write That's one part instead of two. With the
proto-space limitation I have that's an important consideration. All the
while, I've been harping on this notion that there must be SOME drives that
provided this 8-bit option, else it wouldn't have been in the standard at
all. The fact that it was not popular at all is grounds for its removal in
the 1996 standard, but as I say, I want to consider it a possibility until
I'm sure it won't work out. That would make my board a channel board rather
than a device-specific board. I like that notion as well. I won't have to
add any extra parts to those already in the artwork, thereby saving space
that can be used for connectors, and I won't have to put parts on an
external board, because the target devices use the channel as their
interface. It's a goal which I'm exploring. If I come up completely empty
in my search for IDE drives that actually support the 8-bit mode, I can
still use "normal" 16-bit IDE by putting in the circuit that works with
Tilmann Reh's GIDE hardware. I'd leave out the RTC/calendar function,
though, since I use an MSM5832 from OKI for that, having built a board back
in the '80-'81 timeframe for that.
I consider the "correct" parts count to be either 0 or 1. In the case of
the WD100x channel, it's 0, and in the case of the 8-bit IDE it's 0. If it
becomes 1, it has to be a CPLD because I can put all thenecessary registers
and buffers in there without increasing the space that's used.
Now, you've listed a couple of FPGA's. Those inherenly imply a parts count
of 2, unless you load them from your processor. I suppose it's splitting
hairs, but the parts count is really not the issue, it's the space, in my
case, because the board has only those two teensy proto-areas, one at 20 x
12 holes, and the other at 24 x 11. That's barely enough for a 68-pin
PGA/PLCC socket. Few parts come in those packages any more, so the 44-pin
PLCC might be what's left. I do have bigger wirewrap areas on other WW
boards, but this one is so close ...
Frankly, I wish the current generation XILINX software would support the
2000 and 3000 series parts, but the former was end-of-lifed some 10 years
ago and the 3000 has been replaced with the 3000-A series and 3100 series.
The 3030 would make my job MUCH simpler, but I just can't use one due to
software incompatibility.
That's how they get us to buy more parts and throw out the old ones, doncha
know!
----- Original Message -----
From: <allisonp_at_world.std.com>
To: <classiccmp_at_classiccmp.org>
Sent: Wednesday, April 19, 2000 6:42 AM
Subject: Re: 8-bit IDE
> On Tue, 18 Apr 2000, Richard Erlacher wrote:
>
> > Please see itemized comments below.
>
> PLEASE EDIT YOUR MESSAGES, IF I CAN ON A SLOW TELNET LINK YOU CAN!
>
> > > Didnt' say you didn't need the latch only you didnt need an extra FF
to
<snip>
>
> You do not have to explain it to me, I've done it, have working examples!
>
> Allison
>
>
Received on Wed Apr 19 2000 - 09:59:40 BST