[SI-LIST] Re: A question about XTK


Hi Perry:

To my understanding in order to produce an eye pattern providing comprehensive
SI and timing data at the input of a receiver, it is often necessary to apply a 
pseudo-
random bit pattern at the output of the the driver.

Use of .sif file with RANDOM option provides a simple way of accomplishing 
this objective  in XTK simulations.  The XTK/TLC manual states, " By using
the RANDOM option, each edge defined by the PERIOD, %HIGH and CYCLES
statements uses a random bit to determine if the edge will be rising or falling
The first cycle is always RISING then FALLING."

It is interesting to note that the pattern produced by the .sif RANDOM
feature repeats after a 2**32 cycles so that the bit pattern is pseudo-random.

It should be also noted that sometimes a very large CYCLES number is 
desirable to achieve most accurate eye diagrams. In the example .sif file given
in my previous post, the number of CYCLES was set at 200. I have also
used cycles numbers exceeding several thousands but the draw back
is that simulation speed is then significantly reduced.

Regards,

Abe

-----Original Message-----
From:   Perry Qu [SMTP:Perry.Qu@xxxxxxxxxxx]
Sent:   Monday, November 18, 2002 2:09 PM
To:     'si-list@xxxxxxxxxxxxx'
Subject:        [SI-LIST] Re: A question about XTK


Thanks, Abe. What exactly is "Random" option trying to accomplish ? Does it 
give us
the random bit pattern ?

I tried the "eye diagram" option in the new XTK/Eplanner on UNIX without using 
SIF.
The "eye" does not look as expected as what we have in HSPICE, where a 
user-defined
PRBS excitation is used.

Regards

Perry

Abe Riazi wrote:

>      Perry Qu  Wrote:
>
>        Hi, Abe:
>
> I'm interested to know how to do this in SIF also. Could you give a short
> example showing the syntax in SIF to generate a pseudo-random bit pattern ? 
> I'm
> interested in this mainly for pre-layout simulation in scratchpad.
>
> THanks
>
> Perry
>
> >
>
> Hi Perry:
>
> Here is an example .sif file utilizing the RANDOM option:
>
> Netname PERIOD: 10 %HIGH 50 CYCLES: 200 RANDOM OFFSET: 0.0 JTTER: 0.0
>
> Using a recent Nutcracker version of XTK (on a Windows NT
> platform),  I have been able to select any driver of the net and then
> produce an eye pattern at the input of a desired receiver.  As noted in my
> ea rlier post, the eye pattern can reveal information related to ringback, 
> jiiter,
> min/max slew rates, source synchronous timing, etc.
>
> Best Regards,
>
> Abe Riazi
> ServerWorks


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