Do we have a terminology issue here? "Flight time", as I have always understood it, is the delay from the driver's output to the receiver's input, as compared to the driver's delay into the reference load. Simplistically, flight time is the number you add to the driving device's Tco value to figure out the delay from the clock to when the receiver's input switches. (Yes, I know it can be more complicated than that, but I'm being unusually brief). The propagation VELOCITY of a Tline is a property based primarily, as you say, on the surrounding dielectric. The propagation DELAY of a Tline depends primarily on the dielectric constant of the surrounding material and the length of the line. Bottom line, I think when I say "flight time" and you say "interconnect delay", we talking about approximately the same things. "Flight time" specifically includes the idea of adjustment with respect to a reference load, which the "driver input->interconnect->receiver o/p" methodology doesn't need to deal with. As for the ability to model the whole path as you mention, well, I guess that depends on what models the silicon vendors are willing to give us, doesn't it? But yes, I'm familiar with the technique and understand the need to do just that as edge rates increase. Thanks, Todd. Todd Westerhoff SI Engineer Hammerhead Networks 5 Federal Street Billerica, MA 01821 twester@xxxxxxxxxxx ph: 978-671-5084 -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Venkataraman, Srinivas Sent: Tuesday, August 07, 2001 2:07 PM To: Coleman, Dave; 'we_r_frendz@xxxxxxxxx'; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Question about Simulation in Spectraquest Importance: High The flight time will always remain the same and has nothing to do with a well or poorly behaved t-line. Whether the flight time is fast or slow depends only on the dielectric constant of the substrate. This confusion is caused because you are trying to bucket the driver delay, receiver delay and the interconnect delay in different bins. The best way would be to model the whole path, driver input->interconnect->receiver o/p and then quantify the impact of fast and slow skew corners of the devices. Srinivas -----Original Message----- From: Coleman, Dave [mailto:dave.coleman@xxxxxxxxx] Sent: Tuesday, August 07, 2001 7:44 AM To: 'we_r_frendz@xxxxxxxxx'; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Question about Simulation in Spectraquest Rahul, For a well-behaved transmission line circuit, you are correct - the fast corner conditions will yield the min flight time. If you have a not-so-well-behaved circuit (i.e., have signal ringback across threshold), the fast corner conditions may cause the signal to settle later than for the slow corner conditions, so you CAN get a larger flight time with the fast corner conditions. Dave -----Original Message----- From: whiz kid [mailto:we_r_frendz@xxxxxxxxx] Sent: Monday, August 06, 2001 8:14 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Question about Simulation in Spectraquest Hi Gurus, I have a question about the usability of the values that spectraquest spits when doing a flight time simulation. When I am doing a simulation with a fast driver, fast transmission line, and fast reciever I am more concerned with the Min switch time (Min flight time). Is the settle time (max flight time) that SQ displays a use ful parameter here??. Because to find the max flight time u make use of the slow driver, slow line, slow reciever. Am I missing some thing in how to interpret the values. Regards, Rahul. __________________________________________________ Do You Yahoo!? Make international calls for as low as $.04/minute with Yahoo! 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