HP Surestore 28/48-Slot with DLT7000 Digital Linear Tape SCSI-2 Drive and SCSI - Page 33

SCSI Command Overview Library Control Commands Wide Data Transfer Request (WDTR) 03H, The message format is as follows: Byte 0 Byte 1 Byte 2 Byte 3 Extended Message = 01H Extended Message Length = 02H WIDE DATA TRANSFER REQUEST = 03H Transfer Width Exponent = 00H A SCSI device initiates a Wide Data Transfer Request (WDTR) message exchange whenever a previously arranged transfer width agreement may have become invalid. The agreement becomes invalid after any condition that leaves the data transfer agreement in an indeterminate state including: • A hard reset condition • A BUS DEVICE RESET message • A power cycle The WDTR message exchange establishes an agreement between two SCSI devices on the data path width used for Data phase transfers. Since this agreement only applies to Data In and Data Out phases, all other information transfer phases will use an eight-bit data path. Chapter 1 1- 9