Minutes of SPI-2 / EPI Working Group - May 6, 1996

Lohmeyer, John JLOHMEYE at cossymwest.co.symbios.com
Wed May 22 08:33:00 PDT 1996

* From the SCSI Reflector, posted by:

Minutes of SPI-2 Working Group                          X3T10/96-166r2

Accredited Standards Committee*
X3, Information Technology
                                              Doc. No.: X3T10/96-166r2
                                                  Date: May 22, 1996
                                               Project: 1142-D
                                             Ref. Doc.:
                                              Reply to: John Lohmeyer

To:       Membership of X3T10

From:     Bill Ham, SPI-2 Technical Editor
          Ralph Weber, Secretary X3T10
          Larry Lamers, Vicechair X3T10
          John Lohmeyer, Chair X3T10

Subject:  Minutes of SPI-2 / EPI Working Group
          May 6, 1996 -- Ft. Lauderdale FL


1. Opening Remarks

2. Approval of Agenda

3. Attendance and Membership

4. LVD Topics
  4.1 Test Data (96-141) [Ham]
  4.2 LVD SCSI Driver Specification Presentation (96-145r0) [Moore]
  4.3 Standing Waves [Bridgewater]
  4.4  Glitch Avoidance on Selection and Reselection Timeouts  (96-
     158r0) [Lohmeyer]
  4.5 Transmission Line Model (96-___r0) [Gingerich]
  4.6 Timing Budget [Ham]
  4.7 Hot Plugging [Ham]
  4.8 SPI-2 Document Review (X3T10/1142D) [Ham]
     4.8.1 Document Strategy [Milligan]

5. EPI Topics
  5.1 SCSI Bus Arbitration Fairness (Lohmeyer)
  5.2 Document Review (Ham)

6. Summary of Meeting Results

7. Meeting Schedule

8. Adjournment

                          Results of Meeting

1.   Opening Remarks

John Lohmeyer, the X3T10 Chair, called the meeting to order at 9:09
a.m., Monday May 6, 1996.  He thanked Norm Harris of Adaptec for
hosting the meeting.

As is customary, the people attending introduced themselves and a copy
of the attendance list was circulated.

2.   Approval of Agenda

The agenda was approved with the following additions:

     4.8.1 Document Strategy [Milligan]

3.   Attendance and Membership

Attendance at working group meetings does not count toward minimum
attendance requirements for X3T10 membership.  Working group meetings
are open to any person or organization directly and materially
affected by X3T10's scope of work.  The following people attended the

         Name          S        Organization         Electronic Mail   
 ---------------------- -- -------------------------   
Mr. Norm Harris        P  Adaptec, Inc.   
            nharris at eng.adaptec.com
Mr. Tak Asami          A# Adaptec, Inc.             asami at itc.adaptec.com
Mr. Richard Moore      V  Adaptec, Inc.   
            richard_moore at corp.adaptec
Mr. Wally Bridgewater  V  Adaptec, Inc.             wally at eng.adaptec.com
Mr. George Preputnick  V  AMP, Inc.                 gpreputn at amp.com
Mr. Ron Roberts        A  Apple Computer            rkroberts at aol.com
Mr. Borden Moller      V  CMD Technology            borden at cmd.com
Mr. Louis Grantham     P  Dallas Semiconductor      grantham at dalsemi.com
Mr. Siegfried Schmalz  V  Dallas Semiconductor      schmalz at dalsemi.com
Dr. William Ham        A# Digital Equipment Corp.   
  ham at subsys.enet.dec.com
Mr. Ralph O. Weber     P  ENDL Associate            roweber at acm.org
Mr. George Penokie     P  IBM Corp.   
                gop at rchvmp3.vnet.ibm.com
Mr. Dan Colegrove      A# IBM Corp.   
                colegrove at vnet.ibm.com
Mr. Dean Wallace       P  Linfinity Micro   
          75671.3443 at compuserve.com
Mr. Edward A. Gardner  P  Ophidian Designs          gardner at acm.org
Dr. Akira James Miura  A  Panasonic Technologies,   miura at tadw.research.
                          Inc                       panasonic.com
Mr. Skip Jones         P  QLogic Corp.              sk_jones at qlc.com
Mr. James McGrath      P  Quantum Corp.             JMCGRATH at QNTM.COM
Mr. Gene Milligan      P  Seagate Technology        Gene_Milligan at notes.
Mr. Gerald Houlder     A  Seagate Technology        Gerry_Houlder at notes.
Mr. Dave Guss          P  Silicon Systems, Inc.   
    dave.guss at tus.ssi1.com
Mr. Robert N. Snively  P  Sun Microsystems Computer   
bob.snively at eng.sun.com
Mr. John Lohmeyer      P  Symbios Logic Inc.   
       john.lohmeyer at symbios.com
Mr. Pete Tobias        A  Tandem Computers   
         tobias_pete at tandem.com
Mr. Kevin Gingerich    V  Texas Instruments         4307725 at mcimail.com
Mr. Kenneth J. Hallam  P  UNISYS Corporation   
       ken.hallam at mv.unisys.com
Mr. Paul D. Aloisi     P  Unitrode Integrated       Aloisi at uicc.com
Mr. Douglas C.         V  Wolf, Greenfield, and     ddoskocil at wgslaw.com
Doskocil                  Sacks
Mr. Tom Sullivan       V  Wolf, Greenfield, and

29 People Present

Status Key:  P    -  Principal
             A,A# -  Alternate
             O    -  Observer
             L    -  Liaison
             V    -  Visitor

4.   LVD Topics

     4.1  Test Data (96-141) [Ham]

Bill reported that he had no new test data since the data presented at
the previous meeting, two weeks ago.  He offered to (and did) repeat
the presentation for those not present at the last meeting.

Bill's bottom line point was that the transmission line properties of
the bus segment are very important (especially for drivers with
rise/fall times less than 1 ns).  Using normal SCSI cable the device
load spacing should be limited to not less than to 8 inch centers,
i.e. at least 8 inches between connections to the bus.  Using
backplane applications where the capacitance per foot is higher the
spacing may be reduced to 4".  15 meter overall lengths were shown to
have good signal integrity with maximum loading per the above
formulas.  Only cable data presently exists.  The backplane spacing
recommendation extrapolates from the cable data.

These rules are written in the latest revision of SPI-2 (rev 07).

     4.2  LVD SCSI Driver Specification Presentation (96-145r0) [Moore]

Richard presented his latest driver requirements information.  The
requirements were discussed at length and modified slightly.  The
result was a set of curves that define the driver test performance
requirements and significantly tighten the requirements on driver
asymmetry.  Detailed discussions were held between TI and Adaptec and
a mutually agreeable set of requirements resulted.  These will be
placed into rev 08 of the SPI-2 document.

     4.3  Standing Waves [Bridgewater]

Wally requested that the discussion of standing waves be deferred
until the July meeting.

     4.4  Glitch Avoidance on Selection and Reselection Timeouts   

John presented a list of conditions under which release glitches can
occur.  Bill noted that a proposed change in the handling of the REQ
signal during bus release has been included in revision 7 of the SPI-2
document.  This left a third case, that occurs during selection and
reselection.  John described two options for handling the third case
and Bill agreed to add the needed wording to the applicable section of
the SPI-2 document revision.

     4.5  Transmission Line Model (96-___r0) [Gingerich]

Kevin presented a table summarizing several specific cases and results
|from his transmission line model.  The agreements resulting from item
4.2 were compared against this model and a final set of Excel curves
were generated for inclusion in Rev 08.

     4.6  Timing Budget [Ham]

Bill asked that the timing budget topic be removed from the agenda as
this was covered in detail at the last meeting.  He noted that any
discussion of the timing budget can be handled as part of the document

     4.7  Hot Plugging [Ham]

Bill reviewed the hot plugging discussion that occurred at the last
meeting.  The group discussed the history of hot plugging solutions
and how they might or might not apply to LVD SCSI.  Substantial
problems were discussed regarding hot plugging on active busses.

Two active bus protection options were discussed: 1) implementation of
an error checking scheme, such as LRC or CRC; or 2) implementation of
physical bus isolation schemes using multiple segments.  In the
absence of one of these two protection schemes, Bill stated that bus
activity must be stopped before a hot plugging action can be

It was recommended that SPI-2 document the hot plugging cases that are
feasible and not try to introduce special error detection/correction
schemes into the protocol.

     4.8  SPI-2 Document Review (X3T10/1142D) [Ham]

Bill led a review of revision 7 of the SPI-2 document.  He started at
clause 9 and worked to the end of the document.  This started the
discussion at the timing requirements.

Timing budget, clause 9, fig 15:

Gene Milligan asked why the test data pattern was not specified.  He
stated that changing the data pattern could allow folks to pass the
test without meeting the standard.  After considerable discussion it
was pointed out that effects of the data pattern are implicitly
contained in the definitions for the timings where signal amplitude
effects are included.  The conclusion was to add a statement noting
that the driver test circuit in section 10.1.5 is to be used when
making the timing measurements at the driver.  The definitions for the
timings at the receiver are not affected by test circuits.

Wally Bridgewater proposed that the 16 mV in 10.1.2 be changed to 50
mV based on his simulation of voltage mode drivers.  The need for
asymmetrical drivers is part of the reason for the change.  This will
reduce the ground shift allowed to around 300 mV.  This is really a
driver balance test.  The "balance" in this test really related to the
accuracy of the scaling between the assertion and negation drivers.
It is not clear how the present models for transistor behavior are
written.  This issue is similar to the ability to match the behavior
of transistors on the same die of the same wafer but adds the matching
of the size scaling.  It seems reasonable to assume that one will not
get quite as good a prediction when the scaling is considered.  How
much should be allowed is the key question.  Since the 16 mV assumes
symmetrical drivers the group agreed to accept Wally's increase to 50
mV pending further data.

For similar reasons the test limits in 10.1.6 relating to dynamic
output signal balance will be changed to 100 mV from the present 50

Richard Moore presented  modified values for the driver test limits in
10.1.1 that were less pessimestic than his earlier projections.  Part
of the reason for the changes was the realization that it is really
impossible to have the effects of a loaded bus segment appear
instantly at the driver connector.  There will always be a length of
unloaded cable before reaching the loading effect at the next device.
This prevents requiring a driver from actually driving both ways into
heavily loaded segments.  The revised model will be in the mailing.

The assumptions concerning loading, receiver overdrive and other
important features that lead to the test limits will be added to Annex

Add a new figure to accurately capture the additional constraints and
substantially replaces clause 10.1.1.

Connector wording  in SPI-2 Rev 07 was not challenged:- blesses SCA-2
and VHDCI as SCSI connectors by a reference to EIA documents as the
normative standard..

Leakage requirements for singled-ended were changed to 20 micro amps
to allow the universal transceiver to use the more aggressive silicon

LVD configuration rules  based on last meeting's discussion were
reviewed and accepted.

Term power - LVD should interoperate with single-ended.  May operate
down to 2.7 volts, open system requires 4.0 volts.  Change in
philosophy from what is sourced to what is delivered to terminator.
Needs to be reviewed for next meeting.  Allows use of term power for
other than terminators.  Proposed 500 mA min for two LVD terminators
at 3 volts.

An Annex still needs to be developed for the TERMPWR distribution

Do we want to document a `universal terminator'?  The 20 ohm ground
driver needs an allowance to go to 100 ohms at the terminator.
Inclination to develop a `picture' for the next revision similar to
that used for the universal transceiver.

Tak Asami raised a question on table 10 regarding the signals released
|from active negation.  The wording will be clarified.

Requirements on data and parity not needed because they are clocked by
REQ/ACK.  Add requirement that data and parity are level signals and
aren't released until the data changes or bus free is detected after
entering information transfer phase.  Table 10 needs some flushing out
to be clear on how active negation is used.  Need to check SIP.

Recommendation to accept these changes and generate revision 8.

          4.8.1     Document Strategy [Milligan]

This item was deferred to the plenary on Thursday, May 9, 1996.

5.   EPI Topics

     5.1  SCSI Bus Arbitration Fairness (Lohmeyer)

By agreement of the group, discussion of this topic was deferred to
the SCSI Working Group meeting on Tuesday.

     5.2  Document Review (Ham)

As there was no meeting time left this subject was deferred until the

6.   Summary of Meeting Results

The technical parts of the sections included in SPI-2 rev 07 (as
modified in rev 08) appear to be nearly stable in all areas.  There
are still some residual concerns about the effects of voltage mode
drivers, driver slew rates, and the possibility of resonance
conditions that could result in "standing waves".  Data is expected
before the next meeting on the voltage mode drivers and possibly the
slew rates (Digital at least).

The inclusion of EPI with SPI-2 does not appear to be a good strategy
and Bill Ham requested that these meetings be separated since the
interested parties are largely different people.  This request was not
acted on for the July meeting week, but will be considered for

7.   Meeting Schedule

The next meeting of SPI-2 / EPI Working Group will be Thursday-Friday
June 6-7 in Colorado Springs, CO at the Embassy Suites Hotel (719-599-
9100) hosted by Symbios Logic.  This meeting will focus on the LVD
remaining LVD specifications and a detailed document review.  Another
meeting of this group was requested to be held in conjunction with the
X3T10 plenary week in July (also in Colorado Springs, but at the Red
Lion Hotel, 719-576-8900).

8.   Adjournment

The meeting was adjourned at 6:30 p.m. on Monday May 6, 1996.

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