Quantum DLTtape DLT 4000, Руководство по эксплуатации продукта

Страница: 84 / 300

SCSI Description
3-22 Quantum DLT 4000 Tape Drive
6. Drive reads the DB (7-0, P) signals within one hold time of the transition of
the ACK signal to true.
7. The drive waits at least the greater of these periods before again asserting
the REQ signal:
a) A transfer period from the last transition of the REQ signal to true, or
b) A negation period from the last transition of the REQ signal to false.
8. The initiator waits at least the greater of the following periods before again
asserting the ACK signal:
a) A transfer period from the last transition of the ACK signal to true, or
b) A negation period from the last transition of the ACK signal to false.
3.5.5.3 Signal Restrictions Between Phases
When the SCSI bus is between two information transfer phases, the following
restrictions apply to the SCSI bus signals:
•
The BSY, SEL, REQ, and ACK signals do not change.
•
The C/D, I/O, MSG, and DATA BUS signals can change.
•
When changing the DATA BUS direction from out (initiator-driving) to in
(drive-driving), the drive delays driving the DATA BUS by at least a data
release delay plus one bus settle delay after asserting the I/O signal. The
initiator releases the DATA BUS no later than a data release delay after the
transition of the I/O signal to true.
•
When switching the DATA BUS from in to out, the drive releases the DATA
BUS no later than a deskew delay after negating the I/O signal.
•
The ATN and RST signals can change as defined under the descriptions for
the attention condition (Section 3.6.1) and reset condition (Section 3.6.2).
3.5.5.4 STATUS Phase
The tape drive enters the status phase just once per command unless a retry is
requested by the initiator. The only exception is during error cases when the
device goes immediately to bus free, as defined in the ANSI SCSI-2 specification.
Status bytes the tape drive can return are listed in the following table: