P1394> SBP-2 Targets

Eric Anderson ewa at apple.com
Tue Sep 12 11:50:49 PDT 2000

* From the T10 Reflector (t10 at t10.org), posted by:
* "Eric Anderson" <ewa at apple.com>
Multiple targets, represented by multiple Unit Directories, are
fully allowed by the SBP-2 and 1394 specs.  A computer, in
particular, is likely to publish multiple SBP-2 units for
unrelated purposes.

In principle, multiple targets represented by multiple unit
directories would be fully independent, aside from sharing
a node's characteristics such as node ID and GUID.  In practice
the level of independence depends on the sophistication of
your microcontroller.

I haven't kept up with the 1212r work; it may change the
terminology somewhat.  But I don't believe it adds any
restrictions or limits to what 1394 and SBP-2 allow.  In
particular if you have multiple instance directories, and
each one has a (different) unit directory associated with
it, I believe that would represent multiple targets.

Multiple instance directories, each pointing to the same unit
directory, would be different (if 1212r allows that).  The unit
directory would have a single management agent; each node is
limited to at most one login to that agent (by SBP-2); this would
effectively be a single target.

I'm not sure if I'm on the t10 at t10.org mailing list (or if I can
post to it), by the way.

Eric Anderson
Apple Computer
ewa at apple.com

 >Hi All,
 >Recently I have been involved in some discussions about what
 >constitutes an SBP-2 Target; these discussions have pointed out
 >some areas of the SBP-2 spec that are kind of fuzzy.  I'm posting
 >this question to get an idea of how this issue is viewed by the
 >rest of the industry.
 > target: A node that receives device service or management
 >requests from an initiator....
 >This has been interpreted to mean that there is only one SBP-2 target
 >per node.
 >4.1 Unit Architecture
 >In CSR architecture and Serial Bus terminology, targets implemented
 >to this standard are units.  A Serial Bus node that implements a
 >target has a unit directory in configuration ROM that identifies the
 >presence and capabilities of the target.
 >This implies that each SBP-2 unit directory is a separate target.
 >The case not covered by the SBP-2 specification is the one where
 >there are multiple instance directories each containing an SBP-2
 >unit directory.  Is this one target or multiple targets?  I have
 >been assuming that this represents multiple targets; are my
 >assumptions correct?
 >Chuck Rice
 >Software Engineer
 >Hewlett Packard Company
 >Vancouver Division
 >18110 SE 34th Street
 >Vancouver, WA 98683
 >chuck_rice2 at vcd.hp.com

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