Message Protocol; Table 2.2 Extended Message - Fujitsu MAW3073 SERIES Specifications

Code
(hex.)
01 SYNCHRONOUS DATA TRANSFER
REQUEST
03 WIDE DATA TRANSFER REQUEST
04 PARALLEL PROTOCOL REQUEST
2.1.3

Message protocol

(1) Message implement requirements
All SCSI devices shall implement at least the TASK COMPLETE message. If a logical unit
number (LUN) for input and output operations is specified in the command (CDB), the minimum
I/O operations required on the SCSI bus can be executed without using any message other than the
TASK COMPLETE message.
Also, the SCSI device should implement the MESSAGE REJECT message against inappropriate
message reception. The SCSI device must always implement the MESSAGE REJECT message if
it supports any message other than the TASK COMPLETE message. In addition, the SCSI device
supporting the parity check of SCSI data bus should implement the MESSAGE PARITY ERROR
message.
(2) ATTENTION condition
If SCSI device supports messages other than TASK COMPLETE message, the SCSI device
creates ATTENTION condition or responds to the ATTENTION condition.
To indicate that the TARG can support messages other than TASK COMPLETE message, the
TARG initiates MESSAGE OUT phase in response to ATTENTION condition.
Note:
If the INIT is in the ARBITRATION phase and if it generates an ATTENTION condition, it
shall assert the ATN signal before the SELECTION phase starts. If the INIT is not in the
ARBITRATION phase, it shall asserts the ATN signal when sending an SEL signal.
The TARG starts the MESSAGE OUT phase in response to the ATTENTION condition
immediately after the end of SELECTION phase. It shows that the TARG supports messages other
than the TASK COMPLETE message.
If the TARG starts the INFORMATION TRANSFER phase (other than the MESSAGE OUT
phase) when the INIT has generated an ATTENTION condition in the SELECTION phase, the
INIT should negate the ATN before responding to the first ACK signal. If the ATTENTION
condition is not generated during SELECTION phase, the TARG shall not send any message
except for the TASK COMPLETE message to the INIT.
2-4
Table 2.2 Extended message
Message
Number Transfer
of bytes direction
5
TARG↔INIT
4
TARG↔INIT
8
TARG↔INIT
ATN
release
*
*
*
C141-C011