RE: [N8VEM: 3912] Re: [!! SPAM] [N8VEM: 3908] Use of bus termination cards?

["Andrew Lynch" <lyn...@yahoo.com>]

Hi Bill!  Speaking of S-100, the N8VEM S-100 backplane uses active
termination similar to the early Godbout variety.  The schematic is
available in the S-100 directory on the wiki.  

I suppose the circuit could be readily adapted to ECB.  However, I think I
agree with Wolfgang on this one; for slow and small systems (4MHz and less
than 10 slots) termination is probably unnecessary.  If anyone with a bus
analyzer could do some testing and verify as to how the ECB performs.  I am
certainly interested in finding out myself!

Thanks and have a nice day!

Andrew Lynch
 

> -----Original Message-----
> From: n8...@googlegroups.com [mailto:n8...@googlegroups.com] On Behalf Of
> Bill Beech (NJ7P)
> Sent: Wednesday, June 24, 2009 4:29 PM
> To: n8...@googlegroups.com
> Subject: [N8VEM: 3912] Re: [!! SPAM] [N8VEM: 3908] Use of bus termination
> cards?
> 
> 
> All,
> 
> In the S-100 bus realm we used an active termination - I believe it was
> 470 ohm resistors to an approximately 2.0 volt stiff DC source.
> Termination only on one end of the board.  This forces all boards to
> actively drive both ones and zeros but did match the impedance of the 20
> inch long S-100 bus lines.  It really cleaned up the signals especially
> with the higher speed boards.
> 
> Bill
> 
> dr. wolfgang kabatzke wrote:
> > Michael Haardt schrieb:
> >> Hello,
> >>
> >> I have seen a few bus termination cards, but now I start to wonder:
> >> Shouldn't they be used as a pair, one on each end of the backplane?
> >>
> >> One article I saw mentioned having to use bus termination for ECB bus
> >> speeds of 20 MHz.  That's damned fast for ECB, so the termination card
> >> must do something, but again there is no sign of needing two cards.
> >>
> >> Michael
> >>
> >>
> >>
> >>
> > Hi everybody,
> >
> > I found in my CD-Collection a description of my Siemens-SMP16-System.
> > Ok, I have this text only in German. But You may see on this sheet
> > that SMP16 has a bus-termination. On the left side are the signals on
> > the bus and on the right side is the text.
> >
> > V1 is   pull-up on the PCB (CPU, Memory, etc.=
> > V2 is   massive parts of copper on the PCB
> > V3 is  a mssive copper inlay in the PCB
> > R1 is   3k3-Pull-up on the backplane to +5V (termination)
> > R2 is   4k7-Pull-up on the backplane to +5V
> > RC is  R and C to GND
> >
> >
> >
> > Here you see the termination (in the middle of connector 1 and 2 on
> > the left side.
> >
> >
> >
> >
> > Best regards
> >
> > Wolfgang
> >
> > >
> 
> 
>