Fujitsu MCJ3230SS manual Scsi Messages, Message formats, Message types, Atn

Host Interface

4.4 SCSI Messages

SCSI messages are used to control the SCSI bus operating sequence. This section explains how SCSI messages work.

4.4.1 Message formats

There are three types of message formats. In any format, the first byte of each message is a message code (see Table 4.73).

•	1-byte message:	Only the message code
•	2-byte message:	Message with a message code from 20h to 2Fh. Each 2-
		byte message consists of a 1-byte message code and a 1-
		byte parameter. (The ODD does not support this type of
		messages).

•Extended message: Multiple-byte message with message code 01h. An extended message code and message length are defined in each message.

4.4.2Message types

Table 4.73 lists the types of messages provided by the ODD.

Table 4.73 Types of messages provided by ODD

Message	Message	Byte	Transfer direction	ATN
code (hex)		count		release
00	Command Complete	1	TARG → INIT
	Extended Message	n+2
01	(Synchronous Data Transfer		TARG ←→ INIT	INIT
		(5)
	Request)
02	Save Data Pointer	1	TARG → INIT
04	Disconnect	1	TARG → INIT
05	Initiator Detected Error	1	TARG ← INIT	INIT
06	Abort	1	TARG ← INIT	INIT
07	Message Reject	1	TARG ← INIT	INIT
08	No Operation	1	TARG ← INIT	INIT
09	Message Parity Error	1	TARG ← INIT	INIT
0C	Bus Device Reset	1	TARG ← INIT	INIT
80
↓	Identify	1	TARG ←→ INIT
FF

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