Date:     July 14, 1987

To:       X3T9.2 Working Group

From:     James McGrath
          Quantum Corporation
          1804 McCarthy Blvd
          Milpitas, CA 93035
          (408) 432-1100

Subject:  MODE SELECT command modification

  Purpose: to allow the Initiator to move parameter values between the 
Current, Saved, and Default value sets in a single command.  Currently only 
the path from Current to Saved is defined as an option (via the SP bit).  
Using two Reserved bits in the CDB, the Initiator may now move parameters from 
Default to Current, Default to Saved, or Saved to Current.

  While these functions can be accomplished via a sequence of MODE SELECT and 
MODE SENSE commands, it aids integrators in allowing this feature.

  Designate bit 2 of byte 1 of the CDB for the MODE SELECT command (Direct 
Access) as the Read Default (RD) bit.   

  Designate bit 1 of byte 1 of the CDB for the MODE SELECT command (Direct 
Access) as the Write Current (WC) bit.   

The action to be taken as specified by these bits is the following:

 RD  WC  Action
==============================================================================
 0    0  No action.
 0    1  Read the specified Saved Parameters and Write them to the Current 
         Parameters.  No Parameter List should be specified.  SP must be 0.   
 1    0  Read the specified Default Parameters and Write them to the Saved 
         Parameters.  A Parameter List may be specified.  SP must be 0.
 1    1  Read the specified Default Parameters and Write them to the Current 
         Parameters.  No Parameter list should be specified.  The SP bit may 
         be 1, in which case the new Current Parameters shall be saved.

                                RD = 0, WC = 0, SP = 1
                  |-----------------------------------------|   
                  |                                         |
                  |                                         |
                  V        RD = 0, WC = 1                   |
                SAVED  >---------------------------|        |
                  ^                                |        |
                  |                                |        |
                  | RD = 1                         V        |
                  |                             CURRENT >---|
                  | WC = 0                         ^
                  |                                |
                  ^                                |
                DEFAULT >--------------------------|
                            RD = 1, WC = 1
87-122r0.txt