Quantum 10K II - Manual (Page 359)

Appendix B. SCSI Bus Signal Timing
B–38 Quantum Atlas 10K II Ultra 160/m SCSI Hard Disk Drives
Table B–17 WIDE DATA TRANSFER REQUEST Message — Field Descriptions
Field Description
Transfer Width
The transfer width that is established applies to all logical units on both
SCSI devices. The originating SCSI device sets its transfer width value to
the maximum data path width that it elects to use. If the responding
SCSI device can also accommodate this transfer width, it returns the
same value in its WDTR message. If it requires a smaller transfer width,
it substitutes the smaller value in its message. Valid Transfer Width
values are:
00h 8-bit data transfer path (standard data path width)
01h 16-bit date transfer path (Wide SCSI option)
The drive performs 8-bit data transfers by default. After a hard reset, the
receipt of a WIDE DATA TRANSFER REQUEST message exchange must
take place before wide data transfers can take place. The drive or the
initiator can initiate the WIDE DATA TRANSFER REQUEST message
exchange based on the Initiate Wide Negotiation Mode Bit (see the
section of this manual that discusses the MODE SELECT command’s
“Quantum-Unique Page,” [39h]).