About CD-ROM READ(10) Command

JackChenJC JackChenJC at aol.com
Tue Apr 21 08:55:53 PDT 1998


* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
* JackChenJC <JackChenJC at aol.com>
*
The answer of (a) should be much better because some applications use READ(10)
Command with "Transfer Length=0" to perform the SEEK. It might cause error if
the drive not doing seek operation.

Jack Chen

==========================================================
In a message dated 98-04-17 19:39:15 EDT, you write:

<< > * From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
 > * Gene_Milligan at notes.seagate.com
 > *
 > I am forwarding your memo below to the T10 reflector since T10 is the SCSI
 > committee that deals with Multi Media Command sets (MMC) and (MMC-2).
 
 > "Yukihiko Okada" <okada.yukihiko at z-prj.kenwood.co.jp> on 04/16/98 07:39:40
 > PM
 
 >   Dear Sir,
 >                  About CD-ROM READ(10) command
 > 
 >   We are designing CD-ROM drive now.
 > We have a question about READ(10) command "Transfer Length=0"
 > in page 137 of "ATA Packet Interface for CD-ROMs SFF-8020i".
 >   This command has foot notes as "A transfer length of zero
 > indicates that no logical blocks shall be transferred."
 >   Could you advice us that which interpretation is right about
 > this command, (a) or (b) ?
 > 
 > 
 >       (a) Even if transfer length=0, seek to Logical Block Address
 >            and buffering to drive RAM from medium, then finish.
 
 >       (b) Because of transfer length=0, NO seek operation, and
 >            NO buffering from medium, then finish.
 
 The drive can do what it wants.  The command should not return an 
 error in either case.  For example, if the LBA is not readable, this 
 does not cause an error because no data was requested from that 
 block.
 
 It's even questionable if an error should be generated if the LBA is 
 outside of the range of the medium.  For a Play Audio command of zero 
 length, the command shall succeed no matter what the requested 
 address is.
 
 This is a case where the manufacturer should examine where such a 
 command might be used, and determine from that what results in the 
 most reliable, fastest, or easiest implementation.
 -- 
 Rob
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 Send email for my public key
 
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