Path: utzoo!attcan!uunet!aplcen!uakari.primate.wisc.edu!sdd.hp.com!hplabs!otter.hpl.hp.com!hpltoad!hpcpbla!kev
From: kev@hpcpbla.HP.COM (Kevin Jones)
Newsgroups: comp.periphs.scsi
Subject: Re: What's a poor target to do?
Message-ID: <3250004@hpcpbla.HP.COM>
Date: 9 Jul 90 06:45:32 GMT
References: <363@zds-ux.UUCP>
Organization: HP Computer Peripherals Bristol, UK
Lines: 37

> 1. The target signals a 'data in' phase.
> 2. The initiator detects a parity error in the data, and asserts ATN.
> 3. The target notices that ATN is asserted, and signals
     a 'message out' phase.
> 4. The initiator sends an 'initiator detected error' message.'
> 5. The target detects a parity error in the message.

6. The target continues handshaking message-out bytes until the host
   dropps ATN.
7. The target asserts REQ (whilst remaining in message-out phase),
   indicating to the host it wants the previous message-out bytes to
   be re-sent.
8. The host will re-send the message-out byte(s) (It will re-assert
   ATN if there is more than one byte to send).
9. The target receives the  'initiator detected error' message.
10. The target sends a 'restore pointers' message to the host.
11. The target re-transmits the data-in.
12. The operation completes.

Message-out retry is documented in SCSI 1 and 2. Look at the
"Message Out phase" description in the "Logical Characteristics"
section (5 I think??).


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Kevin Jones.                       | Hewlett Packard Ltd,
                                   | Computer Peripherals Bristol,
kev%hpcpbla@hplb.hpl.hp.com        | Filton Road,
                                   | Stoke Gifford,
Tel: 011 44 272 799910 (ext 22351) | Bristol.   BS12 6QZ.
                                   | ENGLAND.
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