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RE: [N8VEM-S100:1412] S-100 Bus Terminator
Hi Rick! I don't think there is a single bus terminator on/off option
jumper. The bus termination is in the loop with the parallel bus pretty
much no matter what AFAIK.
It is part of my concern about combining the bus terminator with the bus
extender is that is makes both circuits a lot more complicated. It would
also cause problems using the new combined bus terminator/bus extender on
S-100 backplanes with pre-existing bus termination.
The philosophy so far has been one function per board and for the most part
it has served us well. Combining multiple functions in to a single board
really drives complexity and has to be handled carefully.
The bus extender has extra non-IEEE-696 tabs or ears that stick up to
support the board under test. It is kind of a weirdly shaped board with the
implicit intent that a builder would only use it with the cover off.
Thanks and have a nice day!
Andrew Lynch
> -----Original Message-----
> From: n8vem...@googlegroups.com [mailto:n8vem-
> s1...@googlegroups.com] On Behalf Of Richard Thwaites
> Sent: Sunday, February 10, 2013 7:34 PM
> To: n8vem...@googlegroups.com
> Subject: Re: [N8VEM-S100:1412] S-100 Bus Terminator
>
> Andrew and John,
>
> If combining with the extender, would it be feasible to have the
termination
> circuitry switchable in/out - eg by having a single patch point that could
be
> jumpered or switched to isolate the circuit from Vcc and/or ground, so the
> extender could be used with or without on-board termination as needed or
> preferred?
>
> On the form factor concern - would it just be a matter of making the
> extender board about 1cm shorter than IEEE-696, so that the top header
> would not protrude above the normal profile?
>
> Rick
>
> On 11/02/2013 8:04 AM, Andrew Lynch wrote:
> > Hi Jack! Thanks! I am sure we can design a modification to the S-100
> > bus extender board to include the bus terminator. My concern is
> > messing up the bus extender design by introducing the bus termination
> > circuitry. It does make some sense though to roll the bus terminator
> > into the bus extender rather than make a new separate board.
> >
> > I'd like to hear more about what John has to say on the idea. One
> > hitch I see is that the bus extender board is not IEEE-696 form factor
> > compatible and would interfere with closing an S-100 chassis.
> >
> > Thanks and have a nice day!
> >
> > Andrew Lynch
> >
> > *From:*n8vem...@googlegroups.com
> > [mailto:n8vem...@googlegroups.com]
> > *On Behalf Of *Jack Rubin
> > *Sent:* Sunday, February 10, 2013 12:59 PM
> > *To:* n8vem...@googlegroups.com
> > *Subject:* RE: [N8VEM-S100:1394] S-100 Bus Terminator
> >
> > I've always liked the EXTERMINATOR, for the name if nothing else, but
> > I'm not sure that combining termination with an extension card is
> > useful. I tend to want to use an extender that won't disturb the
> > existing system which may or may not already have termination, and if
> > termination is needed, then I wouldn't want to sacrifice an extension
> > card to provide it. I'd rather see a short board which simply provides
> > termination in the minimal amount of space required. The CompuPro
> > active terminator is only about 3 inches high.
> >
> > Jack
> >
> > *From:*n8vem...@googlegroups.com
> > <mailto:n8vem...@googlegroups.com>
> > [mailto:n8vem...@googlegroups.com] *On Behalf Of *Paul Birkel
> > *Sent:* Sunday, February 10, 2013 2:38 AM
> > *To:* n8vem...@googlegroups.com <mailto:n8vem-
> s1...@googlegroups.com>
> > *Subject:* Re: [N8VEM-S100:1375] S-100 Bus Terminator
> >
> > Andrew:
> >
> > Being a congenital penny-pincher, as well as a "tweaker", it strikes
> > me as a lost opportunity to define a PCB like this with *lots* of
> > unused space (and yet sucking up a full S-100 slot). At a minimum,
> > how about filling the remaining space with a through-hole proto-area
> > array? It would/could be accompanied by appropriate regulators along
> > one edge but the setup/layout would be spatially similar to the
> > buffered proto-board (replacing the buffer-area with the line-clamp
> > area). This would leave opportunities for experimenters (with legacy
> > S-100 backplanes) to wire-up small accessory circuits -- else no
> > impact on the termination function?
> >
> > Alternatively, place the bus-terminator circuitry onto the unused area
> > of the bus-extender card and get three-in-one functionality with
> > extension, termination, and probe functions. An example of this
> > approach of combining termination and extension was the VTE100a
> > "EXTERMINATOR"; see:
> >
> > http://maben.homeip.net/static/S100/vamp/cards/VMP%20VTE%20100-
> A%20Ter
> > minator.pdf
> > http://maben.homeip.net/static/S100/vamp/photos/VAMP%20VTE-
> 100%20Exter
> > minator.jpg
> >
> http://maben.homeip.net/static/S100/vamp/photos/VTE%20100a%20Exter
> mina
> > tor.gif
> >
> > If trying to go 3-in-1 ends up running into real estate issues then
> > just combine termination & extension like the VAMP.
> >
> > Another possibility would be to commit all/part of the (above)
> > proposed proto-area to specific generally-useful functions. Two
> > possibilities would be a configurable basic UART serial I/O port
> > and/or a configurable
> > 8 or 16-bit (E)EPROM handling up to 1 MB chips. I believe that
> > someone pointed out recently that it would be useful to have a board
> > with these sorts of basic functions in order "bring-up" legacy CPU
> > PCBs in a minimal configuration. One could possibly swap one of these
> > options for the probe in a 3-in-1 configuration? Unfortunately it
> > seems to me that when including the extension-function that the
> > resulting routing problems when adding something like I/O or ROM might
> > require a lot of accessory over-board wires to effectively provide a
> > (minimal) third connection-plane. So that might not be a good idea.
> > But the VAMP illustrates that termination+extension go together quite
> well.
> >
> > My preference would be to leave the existing probe+extension PCB
> > alone, and instead look towards combining termination, Serial I/O, and
> > (E)EPROM into a single card. This plus legacy CPU and RAM cards would
> > result in a functional system on any "naked backplane". If some RAM
> > could be squeezed into this multi-purpose board, so much the better
> > :->. We have all of these circuits in tested-form, the only issue
> > would seem to be routing. This sort of board would also be useful to
> > a wider audience who could only populate the subsections of immediate
> > need (e.g., not actually use the termination section if employing a
> > self-terminated
> > backplane) -- and this would increase the board-orders and therefore
> > the likelihood that we'll quickly reach a good ROI threshold.
> >
> > The bottom line for me is that a pure termination PCB seems like a
> > lost opportunity. And might not easily reach critical-mass for a
> > board-order :-<.
> >
> > On Sat, Feb 9, 2013 at 9:19 PM, Andrew Lynch <LYN...@yahoo.com
> > <mailto:LYN...@yahoo.com>> wrote:
> >
> > Hi
> >
> > Attached are the schematic and PCB layout files for the S-100 Bus
> > Terminator.
> >
> > Please review and send any changes and/or corrections to me.
> >
> > Thanks and have a nice day!
> >
> > Andrew Lynch
> >
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