Seagate Ultra 320 ユーザーズマニュアル
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Parallel SCSI Interface Product Manual, Rev. A
a. after any bus reset event.
b. after a transceiver mode change reset event.
c. after an Abort Task management function is successfully received by a SCSI target port;
d. after an Abort Task Set management function is successfully received by a SCSI target port;
e. after a Clear Task Set management function is successfully received by a SCSI target port;
f. after a Logical Unit Reset management function is successfully received by a SCSI target port;
g. after a TARGERT RESET management function is successfully received by a SCSI target port;
h. after a Clear ACA Task management function is successfully received by a SCSI target port;
i. after a DISCONNECT message is successfully transmitted from a CSI target port (see Section 4.3.2);
j. after a TASK COMPLETE message is successfully transmitted from a SCSI target port (see Section
b. after a transceiver mode change reset event.
c. after an Abort Task management function is successfully received by a SCSI target port;
d. after an Abort Task Set management function is successfully received by a SCSI target port;
e. after a Clear Task Set management function is successfully received by a SCSI target port;
f. after a Logical Unit Reset management function is successfully received by a SCSI target port;
g. after a TARGERT RESET management function is successfully received by a SCSI target port;
h. after a Clear ACA Task management function is successfully received by a SCSI target port;
i. after a DISCONNECT message is successfully transmitted from a CSI target port (see Section 4.3.2);
j. after a TASK COMPLETE message is successfully transmitted from a SCSI target port (see Section
k. after a DISCONNECT message is successfully received by a SCSI target port when information unit trans-
fers are enabled;
l. after the release of the SEL signal after a SELECTION or RESELECTION phase timeout;
m. after a PPR (Parallel Protocol Request) negotiation in response to a selection using attention condition
m. after a PPR (Parallel Protocol Request) negotiation in response to a selection using attention condition
when information unit transfers are enabled (see Section 4.3.12); or
n. after any successful negotiation that causes information unit transfers to be enabled or disabled.
An unexpected bus free occurs when a SCSI initiator port detects a BUS FREE phase that it does not expect
see 3.1.1.2.
see 3.1.1.2.
The target uses an unexpected bus free to inform the initiator of a protocol error. The target may switch to a
BUS FREE phase at any time, except during an ARBITRATION phase, independent of any attention condition.
BUS FREE phase at any time, except during an ARBITRATION phase, independent of any attention condition.
The target shall terminate the task that was the current task before the BUS FREE phase by clearing all data
and status for that task. The target may optionally prepare sense data that may be retrieved by a REQUEST
SENSE command. However, an unexpected bus free shall not create an exception condition.
and status for that task. The target may optionally prepare sense data that may be retrieved by a REQUEST
SENSE command. However, an unexpected bus free shall not create an exception condition.
The initiator shall terminate the task that was the current task before the BUS FREE phase occurred and shall
manage this condition as an exception condition.
manage this condition as an exception condition.
3.1.1.2
Expected bus free phases
Initiators may expect a bus free to occur after one of the following:
a. after the last SPI command information unit is successfully received by a SCSI target port;
b. after a SPI data information unit is successful received by or transmitted from a SCSI target port;
c. after a SPI status information unit is successfully transmitted from a SCSI target port;
d. after a SPI L_Q information unit, if the SPI L_Q information unit Data Length field is zero; or
e. during a QAS phase.
a. after the last SPI command information unit is successfully received by a SCSI target port;
b. after a SPI data information unit is successful received by or transmitted from a SCSI target port;
c. after a SPI status information unit is successfully transmitted from a SCSI target port;
d. after a SPI L_Q information unit, if the SPI L_Q information unit Data Length field is zero; or
e. during a QAS phase.
3.1.2
Arbitration and QAS overview
Arbitration allows one SCSI device to gain control of the SCSI bus so that it can initiate or resume a task.
There are two methods that a SCSI device may use to arbitrate for the SCSI bus: normal arbitration and QAS
(Quick Arbitration and Selection). Normal arbitration is mandatory and requires the detection of a BUS FREE
phase on the SCSI bus before starting. QAS is optional and, when enabled, requires the detection of a QAS
REQUEST message before starting.
(Quick Arbitration and Selection). Normal arbitration is mandatory and requires the detection of a BUS FREE
phase on the SCSI bus before starting. QAS is optional and, when enabled, requires the detection of a QAS
REQUEST message before starting.