Quantum 10K II - Manual (Page 360)

Appendix B. SCSI Bus Signal Timing
Quantum Atlas 10K II Ultra 160/m SCSI Hard Disk Drives B–39
B.8.24 PARALLEL PROTOCOL REQUEST Message (04h)
The PARALLEL PROTOCOL REQUEST messages are used to communicate a
synchronous data transfer agreement, a wide data transfer agreement, and set the
protocol options between two SCSI devices (Figure B-6).
Bit
Byte
7 6 5 4 3 2 1 0
0 Extended Message (01h)
1 Extended Message Length (06h)
2 Parallel Protocol Request (04h)
3 Transfer Period Factor
4 Reserved
5 REQ / ACK Offset
6 Transfer Width Exponent (m)
7 Reserved QAS_Req DT_Req IU_Req
NOTE: Bits 0 – 3 of byte 7 (IU_Req, DT_Req, and QAS_Req) are collectively known as the
Protocol Option bits, and are defined as such in Table B-18.
Figure B–6 PARALLEL PROTOCOL REQUEST Message — Data Format