[ibis-macro] Let me explain one of the architectures of an Rx CDR
- From: "Walter Katz" <wkatz@xxxxxxxxxx>
- To: "IBIS-ATM" <ibis-macro@xxxxxxxxxxxxx>
- Date: Thu, 14 Apr 2011 17:43:15 -0400 (EDT)
All,
This is one of possibly many CDR architectures. The Rx CDR has a reference
clock that is supplied to it. Suppose this reference clock generates
clocks at the UI. This clock will have several sources of jitter that can
be represented by Rx_Rj, Rx_Sj, and Rx_DCD. In this architecture there is
a delay added to these clock times. This delay can be between 0 UI and 1
UI in increments of UI/32. The amount of delay is controlled by the CDR.
There is jitter introduced by this CDR. The jitter in this delay is
represented by Rx_Clock_PDF, Rx_Clock_Recovery_Mean, Rx_Clock_Recovery_Rj,
Rx_Clock_Recovery_Sj, Rx_Clock_Recovery_DCD. The time that the sampling
latch samples the data therefor includes both the jitter in the reference
clock and the CDR. Thus for statistical analysis, since there are no clock
time to determine the CDR jitter, or where the center of the clock is
relative to the center of the eye of the data at the latch, the EDA tool
should use Rx_Clock_PDF, Rx_Clock_Recovery_Mean, Rx_Clock_Recovery_Rj,
Rx_Clock_Recovery_Sj, Rx_Clock_Recovery_DCD and Rx_Rj, Rx_Sj, and Rx_DCD.
In time domain simulation the CDR distribution is extracted from
*clock_times. If the clock_times generated by the CDR in time domain
simulations does not include the Jitter in the reference clock that the
CDR uses, then Rx_Rj, Rx_Sj, and Rx_DCD jitter needs to be added by the
EDA tool. External clocks can be handled by either passing them into the
Rx AMI_GetWave through *clock_times, or can be represented by using the
parameters Rx_Rj, Rx_Sj, and Rx_DCD.
Does this not explain why there are two sets of jitter parameters and how
they should applied?
Walter
Walter Katz
wkatz@xxxxxxxxxx
Phone 303.449-2308
Mobile 720.333-1107
Other related posts:
