SPI-4 revision 2 KEEP_MCS bit

Elliott, Robert Robert.Elliott at COMPAQ.com
Mon Dec 11 15:36:54 PST 2000


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert" <Robert.Elliott at compaq.com>
*
George added an editor's note in spi4r02 for the Keep Margin Control
Settings bit.

in Section 16.3.11.1:
A maintain margin control settings (KEEP_MCS) bit of zero indicates that the
target shall reset to their default values any margin control settings set
with the margin control subpage of the port control mode page (see 18.1.4).
A KEEP_MCS bit of one indicates that the target shall maintain any margin
control settings set with the margin control subpage.

Editors Note 5 - GOP: There needs to be something said about what the target
is supposed to place in the keep_msc bit on the PPRs response.


I see two options:
a) Target always responds with either: 
    0 = not capable of keeping settings
    1 = capable of keeping settings

b) Value is negotiated like most other fields.
  initiator sent a 0:
    0 = target will not keep settings
    1 = illegal
  initiator sent a 1:
    0 = target cannot keep settings, initiator must assume they are volatile
    1 = target agreed to keep settings

I suggest option b).  Here is some wording based on the RTI bit's wording:

A keep margin control settings (KEEP_MCS) bit of zero received by a target
indicates that the target shall reset to their default values any margin
control settings set with the margin control subpage of the port control
mode page (see 18.1.4) and that the target shall respond with the KEEP_MCS
bit set to zero. A KEEP_MCS bit of one received by a target indicates that
the target should retain its margin control settings, and shall respond with
the KEEP_MCS bit set to one if it retains the settings and zero if it does
not.

---
PC: Robert.Elliott at compaq.com
UNIX: relliott at unixmail.compaq.com
 
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