Scsi Message Support - HP C2488A Technical Reference Manual

SCSI Message Support
The disk drive supports messages received from the Initiator in the following manner:
• Multiple byte message out phases are allowed.
• Any message out may be prefixed with an optional Identify byte.
• An optional number of No-Op message bytes may be embedded in the message out received
by the disk drive prior to the final message byte.
• Only one message type (other than the Identify prefix and the optional N o-Op bytes) will
be accepted per message out phase. If more than one type is received, the message will be
treated as an illegal message.
• A maximum of 16-message out bytes will be accepted by the disk drive. if the ATN line is
still set after 16 bytes have been received, the disk drive will treat this as an illegal message
type, except that the disk drive will always terminate in a Bus Free state.
The following message types are supported:
Message Parity Error
Initiator Detected Error
Abort
Reset
No-Op
Message Reject
DRAFT
1/18/93 09:58
If either of these messages is received from the Initiator, the disk drive
will abort the command in process and set the sense key to Aborted
Command with the sense code set to Initiator Detected Error. If a
valid LUN has been received in an Identify or CDB, and a status phase
has not yet begun, then the command will be terminated with a Check
Condition status; otherwise the Target will go to the Bus Free state.
This message will cause the disk drive to abort the command in
process, clear the Initiator's status and go to the Bus Free state.
This message will cause the disk drive to abort the command in
process, reset to Power On conditions for all Initiators, and go to the
Bus Free state.
This message will be treated as an illegal message type if not followed
by some legal message byte, except when the No-Op message type is
received immediately following a Re-select attempt by the Target. In
this case, the Target will attempt to proceed with the interrupted
re-select phase.
If a Message Reject message is received from the Initiator it will
normally be treated like an Illegal Message. Only if the Target is in the
Message In phase and attempting to send one of the following messages
will it be treated differently.
Disconnect Message
In,
Save Data Pointer
Message.ln~
The Target
will not disconnect and will proceed with the command in process.
This will not prevent the disk drive from attempting to disconnect
from the Initiator at a later time.
Synchronous Data Transfer Message In. The Target will assume that
an asynchronous transfer is expected. This will affect all later data
transfer phases.
SCSI Interface 4·7