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CDU-541 CD-ROM DRIVE SCSI INTERFACE MANUAL
Table 4-1: Message Codes
==============================================================================
Code
Description
Direction
OOh
COMMAND COMPLETE
In
02h
SAVE DATA POINTER
In
03h
RESTORE POINTERS
In
04h
DISCONNECT
In
04h
DISCONNECT
Out
05h
INITIATOR DETECTED ERROR
Out
06h
ABORT
Out
07h
MESSAGE REJECT
In
Out
08h
NO OPERATION
Out
09h
MESSAGE PARITY' ERROR
Out
OAh
LINKED COMMAND COMPLETE
In
OBh
LINKED COMMAND COMPLETE (WITII FLAG)
In
0Ch
BUS DEVICE RESET
Out
80h - FFh IDENTIFY
Out
==============================================================================
Key:
In
=
Target to initiator.
Out
=
Initiator to target.
4.4.3. Messages
The single byte messages (Tabie 4-1) are listed below along with their code
values and their definitions.
COMMAND COMPLETE OOh.
This message is sent from the controller to an
initiator to indicate that the execution of a command (or series of linked
commands) has terminated and that valid status has been sent to the initiator.
After successfully sending this message, the controller will go to the BUS
FREE phase by releasing BSY.
The controller will consider the message
transmission to be successful when it detects the negation of ACK for the
COMMAND COMPLETE message with the ATN signal false.
SAVE DATA POINTER 02h.
This message is sent from the controller to direct
the initiator to save a copy of the present active data pointer for the
currently attached logical unit.
RESTORE POINTERS 03h.
This message is sent from the controller to direct
the initiator to restore the most recently saved pointers (for the currently
attached logical unit) to the active state.
Pointers to the command, data;
and status locations for the logical unit shall be restored to the active
pointers.
Command and status pointers shall be restored to the beginning of
the present command and status areas.
The data pointer shall be restored to
the value at the beginning of the data area in the absence of a SAVE DATA
POINTER message or to the value at the point at which the last SAVE DATA
POINTER message occurred for that logical unit.
4-7
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