home *** CD-ROM | disk | FTP | other *** search
- Newsgroups: comp.sys.amiga.hardware
- Path: sparky!uunet!decwrl!deccrl!news.crl.dec.com!pa.dec.com!ninja!zowie.zso.dec.com!ridder
- From: Hans Ridder <ridder@zso.dec.com>
- Subject: Re: LUN 1 SCSI device
- Message-ID: <1992Aug12.181235.1466@ninja.zso.dec.com>
- Originator: ridder@zowie.zso.dec.com
- Sender: news@ninja.zso.dec.com (USENET News System)
- Nntp-Posting-Host: zowie.zso.dec.com
- Organization: Digital Equipment Corporation - DECwest Engineering
- References: <1992Aug11.072220.18797@walter.cray.com> <1992Aug11.203905.11589@ninja.zso.dec.com> <1992Aug12.092722.8257@walter.cray.com>
- Date: Wed, 12 Aug 1992 18:12:35 GMT
- Lines: 30
-
- In article <1992Aug12.092722.8257@walter.cray.com> paws@spam.cray.com (Daniel Baehr) writes:
- > In the most receint copy of the spec that I have they call the LUN
- > what we call the SCSI ID and the SCSI ID is the address present on the
- > databus when a device needs attending to. I thought the definition of
- > LUN we were using was more inline with the way I*M uses it?
-
- Perhaps you're confused by the SCSI vs. IBM use of the term LUN. I'm
- (currently) looking at a SCSI II spec, rev. 10H, but all the SCSI
- specs. I've ever seen documented LUNs and SCSI ID pretty much the same
- way (and as different things.)
-
- SCSI ID is used to select one of the 8 devices on the SCSI bus. LUN is
- used to select one of the 8 "logical units" within a particular SCSI
- device (e.g. a multi slot tape drive.)
-
- The Logical Unit Number (LUN) is in the high-order three bits of the
- second byte of every Command Data Block (CDB) sent on the SCSI bus. The
- SCSI ID does *not* appear in the CDB, it appears as a single SCSI bus
- data line set to a logical 1 state during the Arbitration Phase (if
- used) and the Selection Phase of the bus protocol.
-
- Hope that clears things up a bit. (Unless I got something wrong!)
-
- >| Daniel Baehr Work: paws@spam.cray.com Home: daniel_baehr@bearsden.UUCP|
-
- -hans
- --
- Hans-Gabriel Ridder Digital DECwest Engineering
- ridder@rust.zso.dec.com Bellevue, Washington, USA
- {pacbell,pyramid,uunet}!rust.zso.dec.com!ridder
-