Minutes SAS-1.1 PHY WG teleconference March 3, 2005

Mike Jenkins jenkins at lsil.com
Fri Mar 4 12:42:52 PST 2005

* From the T10 Reflector (t10 at t10.org), posted by:
* Mike Jenkins <jenkins at lsil.com>
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 Rob and all,
I believe the impact of skew directly on jitter is small.  I believe a more serious issue is the resulting common mode voltage, which has impact on EMI as well as other signal integrity aspects.  If I've got my trig right, the common mode voltage, Vcmpp, resulting from intra-pair skew, S, of a signal with dif'l voltage, Vdpp, is:
 Vcmpp = Vdpp * sin [ (pi / 2) * (S / 1UI) ],   (approximately, depending on waveshape)
 Hence, 25 ps of skew in a 1600mVdpp, 3Gb/s signal causes 1600*sin[1.57*(25/333)] = 188mVpp of common mode voltage.
Elliott, Robert (Server Storage) wrote:
 I've posted 05-098r0 which proposes slightly increasing the external (InfiniBand-based) cable length intra-pair skew allowance from 20 ps to 25 ps.  The higher the number, the more impact on the jitter budget.
 Cable manufacturers: please investigate what your cables provide today.
Rob Elliott, elliott at hp.com 
Hewlett-Packard Industry Standard Server Storage Advanced Technology 

From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Alvin.Cox at seagate.com
 Sent: Friday, March 04, 2005 12:24 PM
 To: t10 at t10.org
 Subject: Minutes SAS-1.1 PHY WG teleconference March 3, 2005

The minutes are posted at: 

Items of critical concern for next week's meeting: 

New item - Maximum intra-pair skew requirement for external cables. 
Current specification is 20 pS. Is this number achievable? What can the cables be supplied to? What can the receiver devices tolerate? 

05-075r0  OOB Signal Transmitter Requirements [Wanamaker] 

T10/05-079r1     SAS-1.1 Minimum XR/IR Receiver Signal Level for 3Gb SATA Mode [Olawsky] 

05-084r0     SAS 1-1 Compact Connectors (Internal and External) [Neer] 
Proposal posted 2/23/05. It does not include electrical performance requirements. Is this assumed to be the same as the existing tables? SATA I/O adopted the Molex versions as the plan of record on 3/2. 
Rob Elliott has posted an addition item concerning the use of OOB pins. 
Concerns over ability to resolve all issues before SAS 1.1 letter ballot. Rob has details on timing and concerns list. 

See minutes for additional items and details. 

Alvin Cox
 Seagate Technology, LLC
 Tel 405-350-7424
 Fax 405-324-3067
 Cell 405-206-4809
 E-Mail  alvin.cox at seagate.com 

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