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 > > > > > > * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/[email protected] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
