Fujitsu MCP3130SS, MCP3064SS, MCM3064SS, MCM3130SS manual Status phase, Message phase

SCSI BUS

7.6.8 STATUS phase

In a STATUS phase, the TARG requests to transfer status information from the TARG to the INIT. The TARG keeps the C/D and I/O signals true and the MSG signal false during REQ/ACK handshaking in this phase.

7.6.9 MESSAGE phase

The MESSAGE phase is divided into MESSAGE IN and MESSAGE OUT phases depending on the direction of message information transfer. In either phase, more than one message can be transferred. The first byte transferred in a MESSAGE phase must be a single-byte message or the first byte of a multiple-byte message. If the message consists of more than one byte, all bytes must be transferred in a single MESSAGE phase. For details of message types and their operation, see Chapter 5, "MCD3130SS, MCE3130SS, MCK3130SS, MCM3064SS, MCM3130SS Optical Disk Drives SCSI Logical Interface Specifications."

(1) MESSAGE IN phase

In a MESSAGE IN phase, the TARG requests to transfer message information from the TARG to the INIT. The TARG keeps the C/D, I/O, and MSG signals true during REQ/ACK handshaking in this phase.

(2) MESSAGE OUT phase

In a MESSAGE OUT phase, the TARG requests to transfer message information from the INIT to the TARG. The TARG keeps the C/D and MSG signals true and I/O signal false during REQ/ACK handshaking in this phase.

The TARG executes this phase in response to the ATTENTION condition (described in Subsection 7.7.1) created by the INIT, and must remain in the MESSAGE OUT phase.

Note:	When the TARG returns a MESSAGE REJECT message to reject an
	invalid or incorrect message or when the TARG enters a BUS FREE
	phase as directed by a received message or returns a message
	(SYNCHRONOUS DATA TRANSFER REQUEST message, for
	example) in a prompt response to a received message, it can
	terminate the MESSAGE OUT phase regardless of whether the ATN
	signal is true or false.

When the TARG detects a parity error in the received message information, the TARG can request the INIT to retry message transmission by sending a REQ signal after sensing the ATN signal false without having to change the bus phase (that is, while remaining in the MESSAGE OUT phase). Upon receiving this REQ signal, the INIT must retransmit all of the same message bytes that were transmitted in the MESSAGE OUT phase in the same sequence. If the message consists of more than one byte, the INIT must make the ATN signal true before returning the ACK signal for the first byte and must keep it true until the last byte is transferred.

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