April 25, 1988                                          X3T9.2/88-043 Rev. 0


To:       X3T9.2 Membership


From:     Dan Davies, Cipher


Subj:     MODE SELECT Clarifications


At the March Working Group, I accepted an action item to provide clarification 
for two obscure MODE SELECT/MODE SENSE parameters documented in the sequential 
access  device command set.  This proposal provides suggested wording for  the 
two parameters in question as referenced to the SCSI-2 draft, revision 4.


1) ACTIVE FORMAT FIELD (Section 9.3.3., third paragraph, page 9-53)


Delete the current paragraph:

 Active  format  field  indicates the format that is used  to  record  on  the 
medium.                                                                  


Add the following paragraph:

 Active format field indicates which recording format is used when reading  or 
writing data on a logical unit.  This field is only applicable to devices with 
multiple track configurations for a given density code.  

Values for the active format field shall be assigned as follows:

     00h  Use the logical unit's default recording format.
     01h  Use a single track recording format.
     02h  Use a two track recording format.
 03h-1Fh  Use an increasing number of tracks.

IMPLEMENTORS  NOTE:     A logical unit supporting this field may  not  support 
all  possible track configurations for the given density code (e.g.  a  device 
may only support even track group multiples).                                    

2) MEDIUM FORMAT RECOGNITION FIELD (Section 9.3.4., 9th paragraph, page 9-57)


Delete the current paragraph: 

 A  medium  format  recognition byte with a value of 01h  indicates  that  the 
device  is  able  to recognize the format of the medium.   This  requires  the 
ability  of  the  device  to be able to read,  from  the  medium,  all  format 
information related to that medium.  This implies that at some time, prior  to 
the device returning MODE SENSE information, the device has independently read 
that information from the medium.  A value of 00h in this field indicates that 
the  device can not recognize or does not have the ability to read the  format 
off the medium. This requires that the initiator at some time explicitly  read 
that  information from the medium.  Until that time the format information  in 
this field does not necessarily reflect that of the medium's.  Values 02h thru 
FFh are reserved.  This field is valid only in the MODE SENSE command.                                                                     


Add the following paragraph:

 The  medium format recognition field is a nonchangeable value indicating  the 
device's capability to automatically identify the medium format and  partition 
information  when  reading an unknown volume.  This field does not  address  a 
device's capability to identify the recording density of the medium.

Values for the medium format recognition field shall be assigned as follows:

     00h  Logical unit is incapable of format or partition recognition.
     01h  Logical unit is capable of format recognition only.
     02h  Logical unit is capable of partition recognition only.
     03h  Logical unit is capable of format and partition recognition.
 04h-FFh  Reserved.

IMPLEMENTORS  NOTE:  If  a logical unit indicates that it is  not  capable  of 
medium format recognition, the initiator must supply all necessary  parameters 
for the device to identify the specific format.