RE: [SI-LIST] : Clock Jitter

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From: dkhatri (dkhatri@micron.com)
Date: Wed Apr 25 2001 - 08:13:34 PDT


Thank you all for taking time and clarifying my doubts.

-Thanks,
Dirgha

-----Original Message-----
From: Scott McMorrow [mailto:scott@vasthorizons.com]
Sent: Tuesday, April 24, 2001 4:54 PM
To: Todd Westerhoff
Cc: dkhatri; si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : Clock Jitter

Whether to include clock jitter in Setup or Hold calculations depends upon
the source of the data and the source of the clock for the transmitter and
the receiver.

Let Clock(N) be the Nth clock edge
Let Clock(N+1) be the (N+1)th clock edge

Whether a (cycle to cycle) jitter is included in Setup and Hold calculations
is dependent upon whether or not

case 1) Transmitter and receiver use clocks derived from the same external
clock source. ( a.k.a. synchronous clocking)
             Data transmitted on Clock(N)
            Data received on Clock(N+1) for setup
            Data held against Clock(N)
            Setup requires jitter to be included in calculation.
            Hold does not require jitter to be included in calculation.

case2) Source synchronous, Transmitter clock and data are created from
same clock source. Receiver uses Clock received from transmitter.
            Data transmitted on Clock(N)
            Data Received on Clock(N) for setup
            Data held against Clock(N-1)
            Setup does not require jitter to be included in calculation.
            Hold requires jitter to be included in calculation.

case3) Clock forwarded from one agent-1 to agent-2 (Some processor memory
systems)
Agent-1 receive clock is a delayed version of clock sent to agent-2
Clock sent trom agent-1 to agent-2. Transmission from Agent-1 to Agent-2 is
the same
as Source synchronous case. For transmission from Agent-2 to Agent-1:
            Data is transmitted on Clock(N) by Agent-2
            Data is received on Clock(N+1) by Agent-1 for setup
            Data is held against Clock(N) by Agent-1 for hold.
            Setup for Agent-1 to Agent-2 path does not require jitter to be
included in calculation
            Setup for Agent-2 to Agent-1 path does require jitter to be
included in calculation.
            Hold for Agent-1 to Agent-2 path does require jitter to be
included in calculation.
            Hold for Agent-2 to Agent-1 path does not require jitter to be
included in calculation.

And as Dave Coleman pointed out, there are other sources of jitter that must
be accounted
for, also. Any jitter induced into a clock signal should be included in
path timing calculations,
as well as crosstalk, coupling, sso induced into the data path.

Finally, if intermediate Phase Locked Loops are used in the clocking path,
then jitter from
these must also be accounted for. And, if clocks to devices on a bus are
sourced by
seperate PLL's , for example with cards interfacing to a bus, then the long
term jitter, or
multi-cycle jitter for these devices must be used.

regards,

scott

--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com

Todd Westerhoff wrote:

> Clock jitter normally does not apply to hold equations because both the > driver and receiver are referencing the same clock edge. > > Todd. > > -----Original Message----- > From: owner-si-list@silab.eng.sun.com > [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of dkhatri > Sent: Tuesday, April 24, 2001 3:45 PM > To: si-list@silab.eng.sun.com > Subject: [SI-LIST] : Clock Jitter > Importance: Low > > Hi all, > I have a question regarding the Clock jitter term. whether we should be > using CLOCK JITTER term in the Hold Equations or not.Can any body please > explain me whether we should or should not use it and why? > > Thanks, > Dirgha Khatri > Simulation Engineer > Micron Technology > > **** To unsubscribe from si-list or si-list-digest: send e-mail to > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > si-list archives are accessible at http://www.qsl.net/wb6tpu > **** > > **** To unsubscribe from si-list or si-list-digest: send e-mail to > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > si-list archives are accessible at http://www.qsl.net/wb6tpu > ****

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