99-119 revision 4, Sequence ID

Gary Dickinson g_dickinson at qlc.com
Thu May 20 15:30:07 PDT 1999


* From the T10 Reflector (t10 at symbios.com), posted by:
* Gary Dickinson <g_dickinson at qlc.com>
*
Gentlemen,

I'm looking for a bit of clarification on details of a "run".

My concern has to do with the following statement in section x1.1 of the 
T10/99-119 revision 4 document:

    "A new run begins with every phase change and every time that ATN is
negated."

Is this statement describing a level or an edge event for ATN? 

If this statement is describing a level, then the Sequence ID will be held
at a value
of zero whenever ATN is negated (which is most of the time).

If this statement is describing a edge event, then the Sequence ID will be
reset to
zero only if ATN was asserted on the previous transfer and is now negated.

Or is this statement describing something quite different?

I've drawn up some timing showing 3 possible interpretations of how the
Sequence ID
might behave during a typical selection event.  Which of the following
timing charts 
matches the intent of the statement in x1.1:

Chart #1 (ATN is a level, ID held at 0 when ATN negated):
          +---------------------------+---------------------------------
 PHASE ---|        MESSAGE OUT        |  COMMAND
          +---------------------------+---------------------------------
       -----+  +-----+  +-----+  +-----+  +-----+  +-----+  +-----+  +---
  REQ\      |  |     |  |     |  |     |  |     |  |     |  |     |  |   
            +--+     +--+     +--+     +--+     +--+     +--+     +--+   
       -------+  +-----+  +-----+  +-----+  +-----+  +-----+  +-----+  +-
  ACK\        |  |     |  |     |  |     |  |     |  |     |  |     |  | 
              +--+     +--+     +--+     +--+     +--+     +--+     +--+ 
                               +-----------------------------------------
  ATN\                         |
       ------------------------+
               
             +--------+--------+--------+--------+--------+--------+-----
SEQ ID ------| 0      | 1      | 0      | 0      | 0      | 0      | 0  
             +--------+--------+--------+--------+--------+--------+-----
               


Chart #2 (ATN is an edge event, ID reset on ACK negation):
          +---------------------------+---------------------------------
 PHASE ---|        MESSAGE OUT        |  COMMAND
          +---------------------------+---------------------------------
       -----+  +-----+  +-----+  +-----+  +-----+  +-----+  +-----+  +---
  REQ\      |  |     |  |     |  |     |  |     |  |     |  |     |  |   
            +--+     +--+     +--+     +--+     +--+     +--+     +--+   
       -------+  +-----+  +-----+  +-----+  +-----+  +-----+  +-----+  +-
  ACK\        |  |     |  |     |  |     |  |     |  |     |  |     |  | 
              +--+     +--+     +--+     +--+     +--+     +--+     +--+ 
                               +-----------------------------------------
  ATN\                         |
       ------------------------+
               
             +--------+--------+--------+--------+--------+--------+-----
SEQ ID ------| 0      | 1      | 0      | 0      | 1      | 2      | 3  
             +--------+--------+--------+--------+--------+--------+-----


Chart #3 (ATN has no effect, ID controlled by phase change):
          +---------------------------+---------------------------------
 PHASE ---|        MESSAGE OUT        |  COMMAND
          +---------------------------+---------------------------------
       -----+  +-----+  +-----+  +-----+  +-----+  +-----+  +-----+  +---
  REQ\      |  |     |  |     |  |     |  |     |  |     |  |     |  |   
            +--+     +--+     +--+     +--+     +--+     +--+     +--+   
       -------+  +-----+  +-----+  +-----+  +-----+  +-----+  +-----+  +-
  ACK\        |  |     |  |     |  |     |  |     |  |     |  |     |  | 
              +--+     +--+     +--+     +--+     +--+     +--+     +--+ 
                               +-----------------------------------------
  ATN\                         |
       ------------------------+
               
             +--------+--------+--------+--------+--------+--------+-----
SEQ ID ------| 0      | 1      | 2      | 0      | 1      | 2      | 3  
             +--------+--------+--------+--------+--------+--------+-----


Thanks In advance,


Gary Dickinson
QLogic Corporation
3454 Harbor Blvd.
Costa Mesa, CA 92626
Tel: 714 668-6638
FAX: 714 668-6616
email: g_dickinson at qlc.com
*
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