SSC/SMC wg minutes, 9/14/95, SoftWriteProt.

Patrick Mercer patrick.mercer at
Tue Sep 19 09:49:41 PDT 1995

        Date:    Sep. 19, 1995
        To:      SSC/SMC, SBC and SPC Working Groups 
        From:    Pat Mercer
        Subject: SCSI-3 Software Write Protect proposal
     This is a proposal to add the Software Write Protect, as defined 
     in SSC, to either SBC or SPC.
     (SSC: SCSI Stream Commands
      SBC: SCSI Block Commands
      SMC: SCSI Media Changer Commands
      SPC: SCSI Primary Commands)
     The SSC/SMC WG 11/14 minutes indicated that "the Prevent/Allow 
     Media Removal command should be in the SPC document as it can be 
     used by tape, disk and CD rom devices."
     I would like to suggest that the same situation applies to the 
     Software Write Protect function.  This function is applicable to 
     both tape and disk drives, and is specifically a desirable feature 
     for removable media disk drives.
     It is unfortunate that I was not able to attend the meeting and 
     bring this up earlier, before the control bit was moved, as 
     indicated by the SSC/SMC WG 11/14 minutes, which contain:
     > 4.5 -  Initiator controlled write protect. (X3T10/95-134r0) 
     > Arlan proposed that the Software Write Protect bit be moved from 
     > the read-write error recovery mode page to the device configuration 
     > mode page.  Ted suggested bit 2 of byte 10 for this use.  The
     > working group recommended that this be approved by the Plenary. 
     I propose that Software Write Protect be specified for both tapes 
     and disks.  I would appreciate some advice, though, as to how it 
     should be done.  I see several possibilities:
     --1.  Restore the SWP control bit to the SSC Read-Write Error 
     Recovery Mode page, and add the SWP bit at the same location to 
     the SBC page.
     A possibility, then, would be to combine the pages, which are 
     compatible and have no conflicts, if the various SBC fields are 
     allowed to be left unused by SSC, and move the results into SPC. 
     I'm not clear if the SBC and SSC specific fields could be 
     detailed in SPC, if they should be listed in SBC and SSC or if 
     the slightly different page definitions should just be left in 
     SBC and SSC.
     --2.  Leave SSC as is and add a Device Configuration page to 
     SBC, using the SSC location for the SWP bit (Byte 10, bit 2).  
     The rest of the page would be empty.  This is easy for SSC 
     but doesn't seem the best for SBC.
     --3:  Leave SSC as is and add the SWP bit to the SBC Read-Write 
     error recovery Mode page where it was in SSC.  This would work 
     for both but would result in the same bit defined in two 
     different pages, which doesn't seem too great.
     --4:  ???  Handle this some other way. 
     Suggestions would be most welcome.
     I appreciate your consideration, and please add this as an 
     agenda item for the Palm Springs meeting for SSC, SBC and, 
     if appropriate, SPC.
     Pat Mercer
     SyQuest Technology, Inc.
     47071 Bayside Parkway
     Fremont, CA 94538-6517
     Phone: 510-226-4215  FAX: 510-226-4104 
     Email: patrick.mercer at

More information about the T10 mailing list