September proposals/Timing diagram text

Gene_Milligan at notes.seagate.com Gene_Milligan at notes.seagate.com
Mon Aug 30 07:34:14 PDT 1999


* From the T10 Reflector (t10 at t10.org), posted by:
* Gene_Milligan at notes.seagate.com
*
<<Background:  In figures 46 and 47 (the LVD measurement pictures), there
are some *s on the data signal that note: "use the crossing that yields the
shorter SETUP and HOLD time."  This was done so one picture could show data
going 0 to 1 and 1 to 0.>>

     Perhaps. But the statement also covers the case when due to
noise/crosstalk there is more than one crossing although one was intended.

<< Which 0V crossing is used for the setup and hold timing easurements? >>
     The last one of the data and the first one of the clock. That is
exactly what is meant by "use the crossing that yields the shorter SETUP
and HOLD time." Perhaps crossing should be plural.

I think the suggested additional wording is far too complex. Much of the
detailed discussion is appropriate for design consideration but compliance
measurements should be made with simple test conditions. The designer knows
what allowance has been made for ISI and cable distortion factors. The
timing should be measured with regular patterns producing no ISI and the
result examined for the ISI margin.

I think the statement from the * is adequate and has not caused problems in
the past. The concept has not changed, the numbers have just gotten
smaller.

Gene






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