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> -----Original Message----- > From: Hale Landis [mailto:[EMAIL PROTECTED]] > Sent: Wednesday, January 29, 2003 12:01 AM > To: [EMAIL PROTECTED] > Subject: Re: [t13] ATAPI byte counting > > > This message is from the T13 list server. > > > Pat LaVarre said: ... > > No, only the device knows. A Scsi pass thru protocol > > that lets the device share that info has a > > competitive advantage over a protocol that does not. > > Maybe... But you should take this up with T10 and get them > to define a way for a SCSI device to tell the host how much > data it will transfer (assuming no error). Then come to T13 > and get the ATAPI PACKET command protocol for PIO and DMA > updated to match that capability. The SCSI architecture model requires byte granularity for data transfers by all SCSI transport protocols (see sam3r04 section 5.4.3 - Data transfer protocol services). Parallel, non-packetized SCSI has an IGNORE WIDE RESIDUE message for a target to indicate that the last read data transferred has only one byte rather than two. Parallel packetized SCSI has a data length field in the SPI L_Q information unit describing the size of the following data information unit in byte granularity. Other serial SCSI protocols all have ways to indicate odd lengths (often with a "number of pad bytes" field). If ATAPI lacks this, it's an(other) area where it's not quite SCSI compliant. > > Hale > > *** Hale Landis *** www.ata-atapi.com *** -- Rob Elliott, [EMAIL PROTECTED] Hewlett-Packard Industry Standard Server Storage Advanced Technology
