Quantum 10K II - Manual (Page 339)

Appendix B. SCSI Bus Signal Timing
B–18 Quantum Atlas 10K II Ultra 160/m SCSI Hard Disk Drives
Table B–8 Information Transfer Phases
Signal Direction of Transfer/
MSG C/D I/O Phase Name Definition
0 0 0 DATA OUT Initiator to Drive.
Allows the drive to request that data be sent from the
initiator to the drive.
0 0 1 DATA IN Drive to initiator.
Allows the drive to send data to the initiator.
0 1 0 COMMAND Initiator to Drive.
Allows the drive to request a command from the
initiator.
0 1 1 STATUS Drive to initiator.
Allows the drive to request that status information be
sent from the drive to the initiator.
1 1 0 MESSAGE OUT Initiator to Drive.
Allows the drive to request that message(s) be sent
from the initiator to the drive; the drive invokes this
phase in response to the attention condition created
by the initiator.
The drive handshakes byte(s) until the ATN signal is
negated, except when rejecting a message.
See Message Out — Additional Conditions.
1 1 1 MESSAGE IN Drive to initiator.
Allows the drive to send message(s) to the
initiator.
B.5.5.1 Asynchronous Data Transfer
Drive to Initiator Transfer Procedure
1. The drive drives the DB (7–0, P) signals to their desired values.
2. The drive delays at least one Deskew delay plus a cable skew delay.
3. The drive asserts the REQ signal.
4. The initiator reads the DB (7–0, P) signals.
5. The initiator indicates its acceptance of the data by asserting the ACK signal.
6. When ACK is true at the drive, drive can change or release the DB (7–0, P)
signals.
7. Drive negates the REQ signal.
8. Initiator negates the ACK signal.
9. Drive can continue the transfer by driving the DB (7–0, P) signals and asserting
the REQ signal (steps 1– 3).