[SI-LIST] Re: FW: The standard eye mask test
- From: Vinu Arumugham <vinu@xxxxxxxxx>
- To: chen_jinhua@xxxxxxx
- Date: Thu, 22 May 2003 09:25:43 -0700
a,d) XAUI requires enough samples in the data eye to ensure BER of 1e-12.
c,b) CJPAT and golden PLL or equivalent filtering is required.
Thanks,
Vinu
chen, jinhua wrote:
>Hi,
>
>Since I posted my last message. There is no any public responses.
>And there is not much private responses as well.
>
>Here I forward one of the response. I don't think there is an easy
>Answer to my original question. But we should an industrial standard
>to follow. I don't see a clear description about this issue in FC spec.
>Anybody like to shed more light on this issue?
>
>Thanks!
>
>Jinhua
>
>
>-----Original Message-----
>From: herbert_lage@xxxxxxxxxxx [mailto:herbert_lage@xxxxxxxxxxx]
>Sent: Thursday, May 22, 2003 9:48 AM
>To: chen_jinhua@xxxxxxx
>Subject: RE: [SI-LIST] The standard eye mask test
>
>
>Hi Jinhua,
>
>Since no one seems to have re-plied, I have inquired with our application
>experts for fiber-optics. Please find below our interpretation on how to
>carry out Fibre-Channel jitter measurements. This may not provide a complete
>answer but will hopefully get you started. Please note that some of it may
>strictly speaking only apply to optical eye pattern measurements. Here is
>the response:
>
>
>Fibre channel FC-PI (rev 13 = final) calls out OFSTP-4 (EIA/TIA 526-4A
>Optical Eye Pattern Measurement Procedure, 1997) in clauses 6.2.1 and 6.3.1
>(optical interface specifications). Most of the mask testing will be defined
>in this reference ... except for code pattern.
>
>a.) Number of samples be taken for each test (hundreds/thousands/forever?).
>
> FC-PI (rev 13, now officially an ANSI document) Appendix A,
> Clause A.1.2.1 states "over at least 1000 bit times".
>
> 1000 samples seems to be the most common number in use (at
> various sites) for DCA based eye mask measurements.
>
>b.) What kind of trigger signal used for the test. Use recovered clock
> from CDR, or use golden PLL clock?
>
> FC-PI A.1.2.1 makes a suggestion of a recovered clock (ie. "derived
> from the data stream") but only mandates the use of a bit-rate trigger.
> For the derived clock the document refers to NCITS-TR-25:1999 ("MJS",
> Methodologies for Jitter Specification) for specifics. See clauses
> D2.2 and D2.3 which form the basis of eye mask jitter testing ... an
> issue related to eye mask testing.
>
> For lab testing most companies seem to use the trigger output of a
> BERT tester which is presumed equivalent to a low frequency tracking
> golden PLL.
>
>c.) What kind of data patterns should be used (CJPAT/PRBS or others)?
>
> Fibre Channel FC-PI rev 13 hints at patterns in appendix A.1.2.1
> (by referring to the MJS document). Unfortunately, it appears that
> the MJS document does not specifically advise which of its patterns
> are recommended for eye mask testing.
>
> Our recommended patterns are K28.5 or PRBS 2^7-1 ... as they both
> run from min to max run length (ie. 1-5 bits for 8B/10B). As the run
> length for PRBS is slightly longer it is incrementally more challenging,
> but usually not noticeably so. Using valid 8B/10B traffic is most
> relevant to the application.
>
>d.) Not any eye mask violation can be accepted? Or a few violations can
> be accepted for TX output eye mask?
>
> No violations is pass. One violation is fail. The sample size is
> already quite small to guarantee error free performance.
>
>
>
>Best Regards,
>
> Herbert.
>
>
>-----Original Message-----
>From: chen, jinhua [mailto:chen_jinhua@xxxxxxx]
>Sent: 15 May 2003 22:00
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] The standard eye mask test
>
>
>Hi,
>
>I know there must be someone in the list can give me help in this topic.
>
>The eye mask test is used in a lots standard specs for signal quality test.
>For example, FC standard specified the TX output eye mask and receiver input
>eye mask.
>
>When the eye patterns are measured in the lab, there are so many variations.
>The uncertainty of anyone of those variations can make the test fail or
>pass. Here I list a few variations:
> a.) Number of samples be taken for each test
>(hundreds/thousands/forever?).
> b.) What kind of trigger signal used for the test. Use recovered clock
>from
> CDR, or use golden PLL clock?
> c.) What kind of data patterns should be used(CJPAT/PRBS or others)?
> d.) No any eye mask violation can be accepted? Or a few violations cab
>be
> accepted for TX output eye mask?
>
>In general, is there any STANDARD PROCEDURES to make eye mask measurement
>with those standard specs?
>
>Thanks!
>
>Jinhua Chen
>
>Signal Integrity
>
>EMC Corp.
>
>
>
>
>
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