simple SCSI question

Scott Long scottl at
Mon Jun 18 14:33:37 UTC 2007

emaney wrote:
> iam a student and new to SCSI, i have a question please someone help me to
> get the answer for this
> following question
> how an ‘initiator’ on a SCSI bus identifies the logical entity with which it
> wants to communicate?
> can anyone help me with this question, iam not getting whats is logical
> entity

A parallel SCSI initiator will do two steps to identify the "logical
entity" that it wants to talk to.  First, it'll select the target by
raising a signal on one of the 16 data lines.  Once the target has
responded, the initiator will send a series of 1 or more message bytes
that identify the LUN inside the target that the upcoming command is
for.  This is a gross simplification of how the SCSI wire protocol
works, and I suggest reading some of the docs on for more


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