Section 5
SCSI Programming Guidelines
this time. The NO OPERATION. BUS DEVICE RESET and
ABORT
messages will also function
properly here. All
other
messages will be rejected with a MESSAGE REJECT message.
The IDENTIFY message the initiator sends to the
ProDrive should specify LUN=O.
If
the initiator
supports disconnect/reconnect. it should set bit 6 in the IDENTIFY message.
(See Section 5.6.2.) Unless
bit 6 is set. the
ProDrive will not attempt to disconnect at any point during a command. Bit 6 should not
be set unless the initiator can support receiving the
SA
VE
DATA
POINTER. and DISCONNECT
messages. Upon receipt
of
a legitimate IDENTIFY message, the ProDrive will enter
COMMAND
phase
and begin requesting command bytes from the initiator.
The
ProDrive supports the messages shown in Table 5-2:
TABLE
5-2 Message Codes Supported
By
ProDrive
Code
Description
Direction Supported
<X\i
COMMAND COMPLETE
In
OIH
EXTENDED MESSAGE - SYNCHRONOUS
DATA TRANSFER REQUEST In
Out
02H
SAVE DATA POINTER
In
03H
RESTORE POINTERS
In
04
H
DISCONNECT
In
~
INITIATOR DETECTED ERROR Out
~
ABORT
Out
07H
MESSAGE REJECT
In
Out
08
H
NO
OPERA
nON
Out
00..
MESSAGE PARITY ERROR Out
OAH
LINKED COMMAND COMPLETE
In
OBH
LINKED COMMAND COMPLETE (WITH FLAG)
In
OCH
BUS DEVICE RESET
Out
8~-FFH
IDENTIFY
In
Out
KEY:
In
=
Out =
5.6.2
MESSAGES
The
single byte messages supported by the ProDrive (Table 5-2) are listed below along with their code
values
and
definitions.
COMMAND
COMPLETE
OOH
-
This
message is sent from the ProDrive 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 ProDrive
will
go
into
the
BUS
FREE phase by releasing BSY. This message must be supported by any initiator selecting
the
ProDrive.
NOTE: The completion status
of
the command is indicated in the status byte.
EXTENDED MESSAGE
01H
•
This
message is sent to establish synchronous
data
transfer.
The
message and responses establish the transfer period and the
REQI
ACK offset.
5-10
SCSI
Programming
Guidelines
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