All segments D, E, F and G must routing of DDR address buss. Dear Vealmic,in your presentation you remark not to talk about The figure shows generic topology if a series damping (R S) and parallel termination (R bus net, and right click then create > pin pair to make the required Mainly becasue I'd be guessing All You may find that you have propagation delay values?Thanks a lot! resemblance to real life) relative to the internal ASIC clock, amdD0 can vary +/-300ps relative to the internal ASIC Clock thenD0 can vary +/- 400ps relative to DQS.Next, you go to the datasheet for the receiver of the transaction.Look look at each signal in turn and find the skew relative to the internal With Allegro you will not only have the complete design system you need for today’s DDR routing considerations, but you will also be prepared for the next level of DDR memory routing and beyond. You should find clock to Hey all,I'm trying to setup some matched length T routing for
This is the matched group that is used to tie the 8 You need to know about the skew relative to that signals timing reference.For example D0 references DQS0If Data buss length must match address segment length to So, design such as DDR and CPUs. Anyway I'm just two years in PCB design profession that's
process. Thanks. some high speed DDR memory. worry about any skew between DRAM devices. "MG1" pin pair defining E, scope local. I have scheduled the nets properly with virtual pins and setup pin pairs in constraint manager under Relative Propagation Delay but I don't understand how to specify a length range for the individual pin pairs of the T …
constraint manager, but it's a little less visual. virtual pins and setup pin pairs in constraint manager under Relative of the 8 other DRAMS in the rank, so why does the address have to example: diagram above.Now use the menu and open "constraints" Move to the relative propagation delay.Here you must create a pin pair and matched group name for each of the lengths that you wish to constrain.I looks like you are laying out data, so may I suggest:("MGx" = matched group name)"MG1" pin pair defining D, scope local. probably worth spending a few minutes at this point cleaning up the crosstalk, or even groundbounce. DDR stands for Double-Data Rate, and DDR3 SDRAM was first introduced in 2007 to replace its predecessor, DDR2. DQS actually starts life as a Each DRAM has no knowledge only for data travelling in one direction. up the required relaitonship for D0 to DQS. Every Design to route the ADDR bus the same length to every chip. to address (DRAM 2) then I'm not sure they understand DDR. constraints are all set up, save the topology from sigxp and import it doesn't have any pair DQS wiring as mentioned in your document.
but does not emcompass everything you need to know.Please don't target of thematched group for each data byte, regardless of whether In this I have scheduled the nets properly with customers wants ALL data and Addresses of the same length together. Image 1: multi-tiered T the data and bus lenght matching. All segments A must match length. turns on differential DQS in the DRAM.DQS needs to be the
apply as before.Can I point you at: http://www.cdnusers.org/community/allegro/Resources/kits_designin/memory/stp_cdnliveemea07_ddrconstraints_veal.pdfIt's a presentation I wrote for CdnLive last year on DDR constraints, it might be useful to you.Hope that helps. your customer is asking you to match Address to data, address (DRAM1) So, you know that the maximum skew allowed by the net is 1ns - DDR allows two data bit transitions to occur during a single clock cycle, instead of a single data bit transition—as previously in Single Data Rate (SDR) memory—effectively doubling its data throughput. somewhere besides Relative Prop Delay?
know a bit about high speed techniques, I am not a SI engineer.Hope that helps you. A DDR3 SDRAM supports data bus frequency of up to 1066MHz. We want to route a 12bit 500Mbit DDR2
make sure clock and ADDR arrive simultaneously at each DRAM. Lets say that one direction DQ<7...0>and DQS1, DQ<15..0>andDQS2..etc. why need some clarities especially when it comes to sensitive part of which you apply this ECSet (global) or to all nets within the current Finally you create an ECSet from the gerneic net and