HP Surestore 28/48-Slot with DLT7000 Digital Linear Tape SCSI-2 Drive and SCSI - Page 32

SCSI Command Overview Library Control Commands The extended message length specifies this length plus the number of additional parameter bytes that will follow. The length does not include bytes 0 and 1. An extended message length of zero indicates 256 bytes to follow. Possible extended message codes include the following: 00H 01H 02H 03H 04H-7FH 80H-FFH Modify Data Pointer (not supported) Synchronous Data Transfer Request Reserved Wide Data Transfer request Reserved Vendor unique If the tape drive receives an extended message that it does not support, it switches to the Message In phase and returns MESSAGE REJECT after all the bytes of the message have been transferred. Synchronous Data Transfer Request (SDTR) 01H, This extended message allows the target and initiator to agree on the parameter values relevant to synchronous transfers. The tape drive will not initiate the Synchronous Data Transfer Request message, but relies on the Initiator to do so. The SDTR message has the following format: Byte 0 Byte 1 Byte 2 Byte 3 Byte 4 Extended Message Identifier = 01H Length = 03H Message Code = 01H (SDTR msg) Transfer Period (min=50h max=32h) Transfer Req/Ack Offset (max=15h) 1- 8 Chapter 1