Bevan,

I'd check out Howard Johnson's site at www.sigcon.com and look at his
archives of topics. There are interesting notes such as:

When to use AC Coupling
Three Drop Bus
Hairball Nets
Both-ends Termination
Bus Architecture and Timing
AC Terminators
Bidirectional Terminations
...etc.

Dr Johnson's archive should be able to provide most of the answers you're
looking for. I assume that you don't have access to HyperLynx or similar
simulation tools?

John Haddy



> -----Original Message-----
> From: Bevan Weiss [mailto:[EMAIL PROTECTED]]
> Sent: Friday, 27 September 2002 4:07 PM
> To: Protel EDA Forum
> Subject: Re: [PEDA] OT: termination for a multidrop bidirectional bus
>
>
> The speeds are ~30MHz, the length of the bus is hopefully to be less than
> 12"
>
> The goals are speed, size and cost (high speed, small size, low cost).
> However the speed is pretty much set (30MHz) and the cost is the next
> biggest concern.
> The brands of bus devices used are:
> Epson (S1D13506 LCD controller)
> Motorola MCF5307 microprocessor
> Micron SDRAM
> Fujitsu FLASH memory
> SMSC Ethernet Controller
> Analog Devices AS21065L
> none of these have inbuilt termination resistors, or any form of drive
> control that I know of (please advise me if I'm wrong on this).
>
> The 32bits is pretty much required to maintain bus throughput.  A
> serial bus
> isn't an option.
>
> I'm leaning towards the AC termination method, as that consumes the lowest
> power.  However I'm not too sure whether the rise/fall times
> would be quick
> enough using such a termination method.  Any words of wisdom etc would be
> greatly appreciated, I can't seem to get much info from my
> tutors, it would
> seem it's slightly above most of them :(
>
> Thanks guys,
> Bevan Weiss
>
>
> ----- Original Message -----
> From: "Tony Karavidas" <[EMAIL PROTECTED]>
> To: "'Protel EDA Forum'" <[EMAIL PROTECTED]>
> Sent: Friday, September 27, 2002 5:28 PM
> Subject: Re: [PEDA] OT: termination for a multidrop bidirectional bus
>
>
> > What sort of speed are you running? What length is this bus. What are
> > you goals for the project: speed, size, cost?? Do you need 32 bits?
> > Could you incorporate a serial bus? What brand do you intent to use?
> > Some have series resistors built in (Phillips). Depending on your
> > answers, you could go from no termination to any method you mentioned
> > below. Welcome to the world of engineering and design tradeoffs...
> >
> >
> >
> > > -----Original Message-----
> > > From: Bevan Weiss [mailto:[EMAIL PROTECTED]]
> > > Sent: Thursday, September 26, 2002 9:53 PM
> > > To: Protel EDA Forum
> > > Subject: Re: [PEDA] OT: termination for a multidrop bidirectional bus
> > >
> > >
> > > Hi,
> > > sorry to ask this question to you guys, but I'm more likely
> > > to get an answer from the people dealing with the technology
> > > so to speak...
> > >
> > > What kind of termination is applicable for a multidrop
> > > bidirectional bus (using LVTTL signals)??  I've thought about
> > > series termination, one for each driver on the bus (however
> > > that would total 256 resistors for a 32bit wide bus).  Thus
> > > it's not my preferred method.  I also would prefer to avoid
> > > parallel termination (or thevenin equilavent or ac
> > > termination for that
> > > matter) just because they would take up more inter-trace spacing.
> > >
> > > I'm sure that many of you have had this kind of situation
> > > before and have some advice.  It's for a student design
> > > project and the deadline is quickly approaching.
> > >
> > > Thanks,
> > > Bevan Weiss
> > >
> >
>

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