Chapter 2 Scsi Message; Message System; Message Format - Fujitsu MAN3184 SERIES Specifications

CHAPTER 2
This chapter describes SCSI messages and their operations for controlling the operation sequence of the
SCSI bus.
Note:
The IDD operates as a target device (TARG) on the SCSI bus. The IDD is referred to as the
TARG in this chapter except when its clear identification is required.
2.1

Message System

The message system provides procedures for information (or message) transfer between two SCSI
devices on the SCSI bus in order to control a series of bus phase sequence during command
execution. The messages are transferred over the SCSI data bus in the MESSAGE OUT and
MESSAGE IN phases.
2.1.1

Message format

There are three message formats are listed below. The first byte of the message is a message code
in any format. (See Figure 2.1.)
One-byte message:
Two-byte message:
Extended message:
SCSI MESSAGE
2.1 Message System
2.2 SCSI Pointer
2.3 Message Explanation
This consists of a message code only.
Message code is between X'20' and X'2F'.
message code and one-byte length parameter.
This is a message of multiple bytes length message code of
X'01'.
The Extended message code and message length are specified
in the message.
C141-E123-01EN
This consists of a
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