Josna, In pulse stimulus mode the stimulus will be a square wave at whatever frequency you put in the switching frequency dialogue box. You can also adjust duty cycle if neccessary to model your stimulus waveform. So you need to look at what the switching rate is of the signal or signal group your simulating, not the clock frequency of the interface. Some signals will be at CLK/1, some at CLK/2, etc.. When using custom stimulus patterns the frequency you select is basically the clock frequency of the stimulus generator state machine. In this case you need to spec a 400MHz clock in order to generate a 200MHz square wave stimulus, or any other stimulus with state changes on 25ps boundaries. Basically the clock frequency is twice the highest stimulus frequency. So don't confuse switching rate in pulse mode with clock frequency in custom stimulus mode. You didn't mention which approach you were using so I just wanted to differentiate the two. Brian P. Moran Signal Integrity Engineer Intel Corporation brian.p.moran@xxxxxxxxx -----Original Message----- From: Todd Westerhoff [mailto:twester@xxxxxxxxxxx] Sent: Wednesday, March 13, 2002 5:36 AM To: signalguy@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: SpectraQuest Question. Josna, When you specify a frequency for a "PULSE" stimulus in SQ, it creates a clock of that frequency. So, for example, if you specified "200 MHz", yod get a signal with a 5ns period (2.5ns high, 2.5ns low). I prefer to talk about data rates according to the scheme of the signal used to latch the data. In your case, I'm guessing that you're latching data off the rising and falling edges of a 200 MHz clock signal (also known as Double-Data Rate, or DDR). In that case, you'd specify the data signal as 200 MHz, because SQ simulates it as a clock. In general, the rule for specifying data signal frequencies is: SDR clocking = 1/2 the clock speed DDR clocking = same as clock speed When in doubt, I always just run a simulation and look at the waveforms. If you know how long you expect between data bits, it's easy to figure out whether the setting is right or not. Hope that helps! Todd. Todd Westerhoff Signal Integrity Engineer Hammerhead Networks 5 Federal Street - Billerica, MA - 01821 email:twester@xxxxxxxxxxx - ph: 978-671-5084 ============================================ "I'm starting With the man in the mirror I'm asking him to change his ways And no message could have been any clearer If you wanna make the world a better place Take a look at yourself, and then make a change" - "Man in the Mirror", Michael Jackson -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of fname lname Sent: Tuesday, March 12, 2002 10:08 PM To: 'si-list@xxxxxxxxxxxxx' Subject: [SI-LIST] SpectraQuest Question. Hi folks, I plan to do a simulation on a 400Mhz interface. The data signals toggle at 400Mhz with the two strobes running at 200MHz with base clock at 100MHz. Now when setting up a simulation in SQ do I need to use the clock frequency as 400MHz or 200MHz.I am confused as to if the buffers toggle at 400Mhz or 200Mhz. I would really appreciate If some one can provide more insight into this. Thanks, Josna. 2,000,000,000 Web Pages--you only need 1. Save time with My Lycos. http://my.lycos.com ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu