SCSI Primary Commands - 2.pdf

18 July 2001 T10/1236-D Revision 20The contents of the FIXED bit and STREAM BLOCK LENGTH field are combined with the STREAM DEVICE TRANSFERLENGTH FIELD in the segment descriptor to determine the length of the stream read or write operation as specified intable 26.Table 26 — Stream device transfer lengthsFIXEDbitSTREAM BLOCKLENGTH fieldDescription0 0 Use variable length reads or writes. The number of bytes for each read or write isspecified by the STREAM DEVICE TRANSFER LENGTH field in the segment descriptor.0 not 0 The command shall be terminated with a CHECK CONDITION status. The sensekey shall be set to ILLEGAL REQUEST and the additional sense code shall be setto INVALID FIELD IN PARAMETER LIST.1 0 The command shall be terminated with a CHECK CONDITION status. The sensekey shall be set to ILLEGAL REQUEST and the additional sense code shall be setto INVALID FIELD IN PARAMETER LIST1 not 0 Use fixed record length reads or writes. The number of bytes for each read or writeshall be the product of the STREAM BLOCK LENGTH field and the STREAM DEVICETRANSFER LENGTH field in the segment descriptor.The PAD bit is used in conjunction with the CAT bit (see 7.2.7.1) in the segment descriptor to determine what actionshould be taken when a segment of the copy does not fit exactly into an integer number of destination blocks.All read commands issued to sequential-access type devices shall have the SILI bit equal to zero.NOTE 8 It is anticipated that future versions of this standard may use bit 1 of byte 28 in the device type specifictarget descriptor parameters for stream device types to indicate the value of the SILI bit for read commands, afterT10 establishes how the copy manager is to process tape reads of unknown block length without error.The copy manager shall not read ahead from sources of stream device type. That is, the read operations requiredby a segment descriptor for which the source is a stream device shall not be started until all write operations forprevious segment descriptors have completed.7.2.6.9 Device type specific target descriptor parameters for processor device typesThe format for the device type specific target descriptor parameters for the processor device type (device type codevalue 03h) is shown in table 27.Table 27 — Device type specific target descriptor parameters for processor device typesBitByte7 6 5 4 3 2 1 028 Reserved PAD Reserved2931ReservedThe PAD bit is used in conjunction with the CAT bit (see 7.2.7.1) in the segment descriptor to determine what actionshould be taken when a segment of the copy does not fit exactly into an integer number of SEND or RECEIVEcommands.dpANS SCSI Primary Commands - 2 (SPC-2) 57