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Message Reject
(07 H )
This code is sent from the Initiator or ACB-5500 if the message
received was inappropriate or not implemented.
The Initiator
will assert the ATTN signal prior to its release of ACK for the
REQ/ACK handshake of the message that will be rejected.
When the
ACB-5500 sends this message,
it will change to MESSAGE IN phase
and send this MESSAGE prior to requesting additional message
bytes.
No Operation
(08 H )
This message is sent from an Initiator in response to the ACB-
5500's request for
a message when the Initiator does not
currently have any other valid message to send.
Linked Command Complete
(0AH)
This message is sent from the ACB-5500 to an Initiator to indi-
cate that the execution of a linked command has been completed
and that status has been sent.
The Initiator is then allowed to
set up the pointers for the initial state for the next linked
command.
Linked Command Complete with Flag
(0B H )
This message is sent from the ACB-5500 to an Initiator to indi-
cate that the execution of a linked command (with the FLAG set)
has completed and that status has been sent.
The Initiator is
then allowed to set up the pointers for the initial state of the
next linked command.
Typically the FLAG would cause an interrupt
in the Initiator.
Bus Device Reset
(0C H )
This message can be sent from an Initiator to direct the ACB-5500
to reset all current I/O operations on that BUS DEVICE.
This
message forces the ACB-5500
to an initial state with no opera-
tions pending for any Initiator.
Upon re'cognizing this message,
the ACB-5500 goes to the BUS FREE phase.
Identify
(80 H to FFH)
This code is sent by either the Initiator or ACB-5500 to estab-
lish the physical path connection between the Initiator and ACB-
5500 for a particular disk device (or Logical Unit).
Bit-7 is always set to identify this message.
Bit-6 is set by the Initiator to indicate it is capable of accom-
modating disconnection and reconnection.
500504-00
4-15
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