Wide mode transfer (16-bit SCSI)

The wide mode transfer enables information transfer using a multiple-byte-wide data bus. It is used only in DATA phases.

In wide mode transfer, the WIDE DATA TRANSFER REQUEST or PARALLEL PROTOCOL REQUEST message should first be exchanged by the INIT and the TARG to define the data transfer mode between SCSI devices. When the WIDE DATA TRANSFER REQUEST or PARALLEL PROTOCOL REQUEST message is exchanged, a data bus width is determined. Figure 1.38 shows the data sequence at data transfer. When a wide data transfer agreement is negotiated in PARALLEL PROTOCOL REQUEST data bus width is determined 16 bit mode automatically.

Note:

The IDD supports 8-bit and 16-bit transfer modes. The initial value of the data bus width is "8-bit mode". After power is turned on, a RESET condition occurs, or a TARGET RESET

Number of information items transferred

P cable

1 Unused A “8-bit mode”

2 Unused B

DB15...DB8 DB7...DB0

1 B A “16-bit mode”

Figure 1.38 Data sequence at data transfer

1.6.6 COMMAND phase

The COMMAND phase is a bus phase in which the TARG requests the INIT to transfer command information (CDB) to the TARG. The TARG keeps the C/D signal true and the I/O and MSG signals false during REQ/ACK handshaking in this phase.

1.6.7 DATA phase

The DATA phase is divided into DATA IN and DATA OUT phases according to the direction of data transfer. In a DATA phase, synchronous data transfer can be performed.

(1) DT DATA IN phase

The DT DATA IN phase allows the target to request that data be sent to the initiator from the target using DT data transfers. The target shall assert the I/O and MSG signals and negate the C/D signal during the REQ/ACK handshake(s) of this phase.

(2) DT DATA OUT phase

The DT DATA OUT phase allows the target to request that data be sent from the initiator to the target using DT data transfers. The target shall assert the MSG signal and negate the C/D and I/O signals during the REQ/ACK handshake(s) of this phase.

(3) ST DATA IN phase

The ST DATA IN phase allows the target to request that data be sent to the initiator from the target using ST data transfers. The target shall assert the I/O signal and negate the C/D and MSG signals during the REQ/ACK handshake(s) of this phase.

(4) ST DATA OUT phase

The ST DATA OUT phase allows the target to request that data be sent from the initiator to the target using ST data transfers. The target shall negate the C/D, I/O, and MSG signals during the REQ/ACK handshake(s) of this phase.

(5) Data transfer rate in synchronous mode

Table 1.20 lists the synchronous transfer mode parameters valid for the IDD. The actual values are determined by exchange of SYNCHRONOUS DATA TRANSFER REQUEST or PARALLEL PROTOCOL REQUEST message between the two SCSI devices. If two or more INITs are used, different parameters may be used by each INIT. The PARALLEL PROTOCOL REQUEST message are used to negotiate a synchronous data transfer agreement, a wide data transfer

agreement, and set the protocol options between two SCSI devices. Although the data transfer rate is determined by the Transfer Period parameter, an appropriate REQ/ACK Offset parameter value must be selected depending on the ACK pulse response of the INIT. The interface cable length must also be considered.

Table 1.20 Parameters used for fast synchronous data transfer mode

Transfer rate Parameter type Selectable value

8-bit mode 16-bit mode

X’08’(6.25ns) (5) Maximum 320.00 MB/s X’09’(12.5ns) (4) Maximum 160.00 MB/s X'0A' (25 ns) (3) Maximum 80.00 MB/s X'0B' (37.5 ns) (3) Maximum 53.30 MB/s X'0C' (50 ns) (2) Maximum 40.00 MB/s X'11' (75 ns) (2) Maximum 26.66 MB/s X'19' (100 ns) (1) Maximum 20.00 MB/s X'1F' (120 ns) (1) Maximum 16.00 MB/s X'25' (150 ns) (1) Maximum 13.33 MB/s X'2B' (175 ns) (1) Maximum 11.42 MB/s X'32' (200 ns) Maximum 10.00 MB/s X'38' (225 ns) Maximum 8.88 MB/s X'3E' (250 ns) Maximum 8.00 MB/s X'44' (275 ns) Maximum 7.27 MB/s X'4B' (300 ns) Maximum 6.66 MB/s X'51' (325 ns) Maximum 6.15 MB/s X'57' (350 ns) Maximum 5.71 MB/s PPR Transfer Period (6) X'5D' (375 ns) N/A Maximum 5.33 MB/s X'0A' (25 ns) (3) Maximum 40.00 MB/s Maximum 80.00 MB/s X'0B' (37.5 ns) (3) Maximum 26.60 MB/s Maximum 53.30 MB/s X'0C' (50 ns) (2) Maximum 20.00 MB/s Maximum 40.00 MB/s X'11' (75 ns) (2) Maximum 13.33 MB/s Maximum 26.66 MB/s X'19' (100 ns) (1) Maximum 10.00 MB/s Maximum 20.00 MB/s X'1F' (120 ns) (1) Maximum 8.00 MB/s Maximum 16.00 MB/s X'25' (150 ns) (1) Maximum 6.67 MB/s Maximum 13.33 MB/s X'2B' (175 ns) (1) Maximum 5.71 MB/s Maximum 11.42 MB/s SDTR Transfer Period (7) X'32' (200 ns) Maximum 5.00 MB/s Maximum 10.00 MB/s (1) Fast synchronous data transfer mode (Fast SCSI)

(2) Ultra fast synchronous data transfer mode (Fast-20 SCSI)

(3) Ultra-2 fast synchronous data transfer mode only for LVD (Fast-40 SCSI)

(5) Ultra-320 fast synchronous data transfer mode only for LVD (Fast-80 SCSI). This code is only valid if the PROTOCOL OPTIONS field has a value selected that supports double-transition and information units transfer.

(6) PPR : PARALLEL PROTOCOL REQUEST

(7) SDTR : SYNCHRONOUS DATA TRANSFER REQUEST

Figure 1.39 Data transfer rate in synchronous mode

1.6.8 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.

1.6.9 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, several messages 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, refer to Chapter 2.

(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 Section 1.7.1) created by the INIT, and must remain in the MESSAGE OUT phase.

Note:

The TARG can terminate the MESSAGE OUT phase even when the ATN signal is true when it returns a MESSAGE REJECT message to reject an illegal or invalid message, when it enters the BUS FREE phase as directed by the received message, or when it returns a message immediately in response to a received message (such as the SYNCHRONOUS DATA TRANSFER REQUEST).

The TARG can process a received message immediately if no parity error is detected. If a parity error is detected, the TARG shall ignore all messages which have been received after the parity error detected in the MESSAGE OUT phase.

When the TARG receives all message information correctly without detecting a parity error, the TARG shall enter the INFORMATION TRANSFER phase other than the MESSAGE OUT phase and execute at least one byte of information transfer in order to request the INIT not to retry message transfer. During some message transfer, the TARG may report the normal completion of message reception by switching to the BUS FREE phase (for example, ABORT TASK SET and TARGET RESET messages).