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SCSI Description
Quantum DLT 7000 Tape System 3-25
Table 3–7 Drive MESSAGE OUT Phase Response
ATN Signal True in Phase... The Drive Enters MESSAGE OUT…
COMMAND After transferring part or all of the command descriptor block
bytes.
DATA At the drive’s earliest convenience (often on a logical block
boundary). The initiator continues REQ/ACK handshakes until it
detects the phase change.
STATUS After the status byte has been acknowledged by the initiator.
MESSAGE IN Before it sends another message. This permits a MESSAGE
PARITY ERROR message from the initiator to be associated with
the appropriate message.
SELECTION
1
Immediately after that SELECTION phase.
RESELECTION
2
After the drive has sent its IDENTIFY message for that
RESELECTION phase.
1
Before the initiator releases BSY, provided the initiator asserted ATN
2
The initiator should only assert the ATN signal during a RESELECTION phase to transmit a BUS
DEVICE RESET or DISCONNECT message.
The initiator keeps the ATN signal asserted if more than one byte is to be
transferred. The initiator can negate the ATN signal at any time, except it does
not negate the ATN signal while the ACK signal is asserted during a MESSAGE
OUT phase. Normally, the initiator negates the ATN signal while the REQ
signal is true and the ACK signal is false during the last REQ/ACK handshake
of the MESSAGE OUT phase.
3.6.2 Reset Condition
The tape drive responds to power-on and/or bus reset conditions as described:
• All tape drive SCSI lines assert high impedance when the tape drive is
powered off.
• The drive does not generate any spurious signals on the SCSI bus when the
drive is powered on.
• Within five (5) seconds of power-on, and within 250 milliseconds (typically
under 4 milliseconds) after a bus reset, the tape drive responds to SCSI bus
selections and returns the appropriate normal responses. Tape motion
commands are returned with Check Condition status, Sense Key of Not
Ready, until the medium has been made ready.