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Chapter 4 SCSI Interface

General SCSI Bus Operation

Quantum|ATL PowerStor L500 Series Tape Library User’s Guide 63

• Bus device reset message

• Media may have changed asynchronously

• Another initiator changed the mode parameters

It is not unusual for a firmware (microcode) update to complete

two queued Unit Attentions. The firmware has a limited number

of Unit Attention buffers. If an initiator does not clear queued Unit

Attentions, the library stops generating new Unit Attentions for

that Initiator-LUN (I-L) combination at some point, but existing

ones are left queued.

Behavior Around

Power-On and

SCSI Bus Reset

All device SCSI lines go to high impedance when the library is

powered off.

The library does not generate any spurious signals on the SCSI bus

at power-on.

Within 5 seconds of power on, and within 250 milliseconds

(typically under 4 ms) after a Bus Reset, the library responds to

SCSI bus selections and returns appropriate, normal, responses.

Tape motion commands are returned with Check Condition status,

Sense Key Not Ready, until the media has been made ready.

The Hard Bus Reset option is implemented.

The library recognizes multiple bus resets in succession and bus

resets of arbitrarily long duration. It recovers within the time limits

specified above, following the last bus reset.

Other SCSI

Functionality

Linked commands and untagged queuing are supported.

Bus Phases

The library conforms to the bus state transition table shown in the

SCSI-2 standard, “Phase Sequences.” The information in the

following sections also applies.

1 2 ... 72 73 74 75 76 77 78 79 80 81 82 ... 119 120

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Quantum L500 Guia do Utilizador Página 77