BMQ and ATAPI bridging

David Hawks Hawks at iomega.com
Mon Mar 22 15:11:49 PST 2004


* From the T10 Reflector (t10 at t10.org), posted by:
* "David Hawks" <Hawks at iomega.com>
*
Rod,

Thank you for your response.

> If your device does not support bus termination, it
> could reject a request to drive DIFFSENS in LVD mode
> as well.

Sounds great.  That is just what I was after.

> A bridged device having a different native interface
> would not provide these descriptors (unless it was
> able to represent them as its own perhaps).

I can almost represent SPI as my own.  I have the
capability to set all of the required parameters, I
only lack the capability to query the bridge as to
the current parameters.  I suppose since I cannot
truly represent the interface, I should not provide
the descriptor at all.  Is that the suggestion? If
so, I cannot support the DTD Primary Port descriptor
sub-page at all.  Is that acceptable?

Thank You,
David Hawks


> -----Original Message-----
> From: Rod Wideman [mailto:rod.wideman at adic.com] 
> Sent: Monday, March 22, 2004 9:51 AM
> To: David Hawks
> Cc: T10 at t10.org
> Subject: RE: BMQ and ATAPI bridging
> 
> 
> David,
> 
> I'll take a shot at your questions.
> 
> 1.  Your device should have the option of returning a check condition
> for invalid combinations of BUS MODE and BMQ (e.g., a bus mode of HVD
> and BMQ of 11b).  If your device does not support bus termination, it
> could reject a request to drive DIFFSENS in LVD mode as well.  I see
> that the ADC standard does not currently describe this, so a 
> proposal is
> welcome (from anyone).
> 
> 2.  The ADC standard currently only provides port descriptors 
> for FC and
> parallel SCSI port types in this mode page.  A bridged device having a
> different native interface would not provide these descriptors (unless
> it was able to represent them as its own perhaps).  So, ADC currently
> only addresses FC and SPI devices (not ATAPI, not SAS, etc).
> 
> Rod Wideman
> 
> 
> -----Original Message-----
> From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of David
> Hawks
> Sent: Thursday, March 18, 2004 1:22 PM
> To: t10 at t10.org
> Subject: ADI: BMQ and ATAPI bridging
> 
> 
> * From the T10 Reflector (t10 at t10.org), posted by:
> * "David Hawks" <Hawks at iomega.com>
> *
> I have a couple of ADI questions:
> 
> 1.  
> Table 36 of document 1558-D Revision 6 (ADC) discusses the 
> effect of the
> "bus mode qualifier" field.  This field seems to direct the 
> target port
> to drive or not drive the DIFFSENS line.  According to document 1365D
> revision 10 (SPI-4), terminators drive this line, not 
> devices.  How am I
> supposed to interpret the "bus mode qualifier" field if my LVD device
> does not have an internal terminator?  Can I safely ignore this field?
> 
> 2.  
> Consider an ATAPI device connected through a SCSI bridge.  Suppose the
> ATAPI device cannot control parameters such as "minimum 
> transfer period"
> and bus mode.  Also suppose the ATAPI device cannot determine the
> current transfer period or bus mode.  Does the specification allow for
> such a device?  How does such a device respond when asked to change or
> report said parameters?
> 
> Thank You,
> David Hawks
> *
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