Semi-OT: ISA bus termination
Johannes
the card is everything except audio, which I want to add thru a
SoundBlaster or GUS.
Do I just connect each pin on the ISA socket to the corresponding one
on the other socket? Or do I need termination? If so, how should the
ISA bus be terminated? I know almost nothing about these things. If it
matters, the sockets are going to be close together, probably almost as
close as possible.
I'm also going to feed power thru the ISA socket, that can't be
anything else than just applying it straight to any of the socket pins
can it? (with bypass caps etc. of course)
/J
(I know this group is about MCA but you guys seem to be the only people
left who know this stuff. If there's a more suitable group, please tell
me)
Saskia Bormann
> I'm building a mini-backplane for an industrial-style 486 ISA card. On
> the card is everything except audio, which I want to add thru a
> SoundBlaster or GUS.
>
> Do I just connect each pin on the ISA socket to the corresponding one
> on the other socket? Or do I need termination? If so, how should the
> ISA bus be terminated? I know almost nothing about these things. If it
> matters, the sockets are going to be close together, probably almost as
> close as possible.
If they are only two connectors, connected directly to each other - more
cable-like than bus-like - you definately don't need termination. In the
other case you *may* need one ...
> I'm also going to feed power thru the ISA socket, that can't be
> anything else than just applying it straight to any of the socket pins
> can it? (with bypass caps etc. of course)
Of course. In the normal case, the motherboard would do it with it's own
"backplane". Now you are the "motherboard" designer ;o)
> (I know this group is about MCA but you guys seem to be the only people
> left who know this stuff. If there's a more suitable group, please tell
> me)
Just be sure to run >IBM< OS/2, and you are on topic *g*
Saskia
David L. Beem
> ...If they are only two connectors, connected directly to each
> other - more cable-like than bus-like - you definately don't
> need termination. In the other case you *may* need one ...
You may want to add resistor networks to be certain in the end, especially
if you see errors. For the signals the soundcard actually needs you could
even trim down the lines a little (DMA & IRQ other than what is on the
soundcard).
David
Da...@IBMMuseum.com
Johannes
>Just be sure to run >IBM< OS/2, and you are on topic *g*
Why of course! *looks at yet-to-be-opened shrinkwrapped OS/2 Warp* :-)
>David L. Beem wrote:
>You may want to add resistor networks to be certain in the end, especially
>if you see errors. For the signals the soundcard actually needs you could
>even trim down the lines a little (DMA & IRQ other than what is on the
>soundcard).
What should the resistor networks look like (what values etc) ? And
what do you mean by "trim down the lines" ? Google seems to hate the
ISA bus :-(
I don't have easy access to a multichannel scope or TDR meter, not even
a logic analyzer. So perhaps I better add termination from the start ?
BTW, is there any webpage or something detailing how to build an ISA
card ? I have the signal descriptions etc. but it would be nice with
some DIY guidance as I've never done anything like that before.
/J
UZnal
> BTW, is there any webpage or something detailing how to build an ISA
> card ? I have the signal descriptions etc. but it would be nice with
> some DIY guidance as I've never done anything like that before.
A good introduction, with an example, is found in the book:
M. Sargent/R. Shomeaker/E. Stelzer "Assemblersprache und Hardware des IBM
PC" (orig. The IBM Personal Computer from the Inside Out), Addison-Wesley,
1987.
David Ress
> BTW, is there any webpage or something detailing how to build an ISA
> card ? I have the signal descriptions etc. but it would be nice with
> some DIY guidance as I've never done anything like that before.
Look at:
http://charm.cs.uiuc.edu/users/olawlor/projects/1998/lisa/index.html
for ISA adapter development.
Good luck building a passive backplane.
exwisdem
IBMMuseum
> What should the resistor networks look like (what values
> etc) ? And what do you mean by "trim down the lines" ?
here at the house at the moment. By "trimming the lines" I mean only
connecting the signals the soundcard would use.
David
Da...@IBMMuseum.com
Johannes
FWIW, I also happened to stumble upon this page:
http://www.market.croadria.com/isa_card/atcardTR12.shtml
I ordered the Sargent book yesterday. Looks like I'll really will make
a card after all!
/J