Hitachi HUS151414VL3600, Specifications

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Hitachi Ultrastar 15K147 SCSI Hard Disk Drive Specification
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Table 173: Wide Data Transfer Request
E The Transfer Width Exponent (E) is two to the transfer width exponent bytes wide. Valid data transfer widths are 8
bits (E = 00h) and 16 bits (E = 01h). Value of E greater than 01h are reserved.
19.1.3.1 Transfer Width Negotiation started by the Initiator
If the Initiator recognizes that negotiation is required and sends a Wide Data Transfer Request message out, the Target
responds by changing to the Message In phase and sending a Wide Data Transfer Request message in to the Initiator prior to
transferring any additional message bytes (or any other Information phase bytes) from the Initiator. This provides an interlock
during the data transfer width negotiation.
The drive responds to each Initiator requested transfer width exponent as shown in the following table.
Table 174: Initiator request/Target response
If after the Target's response above the Initiator asserts the ATN signal and the first message received is either a Message Parity
Error or a Message Reject message, the Target negates the data transfer width agreement and goes to 8 bits mode. For the Mes-
sage Parity Error case the implied data transfer width agreement is reinstated if the Target successfully retransmits the Wide
Data Transfer Request message to the Initiator. For any other message the Target completes negotiation and goes to the negoti-
ated data transfer width.
19.1.3.2 Transfer Width Negotiation started by the Target
If the Target recognizes that negotiation is required, the Target sends a Wide Data Transfer Request message to the Initiator
with the transfer width exponent equal to 1 (E = 01h). The Initiator must respond by asserting the ATN signal prior to its
release of ACK for the REQ/ACK handshake of the last byte of the Wide Data Transfer Request message. This provides an
interlock during the wide data transfer negotiation. If the Initiator does not assert the ATN signal, the Target goes to 8 bit
mode. If the Initiator does assert the ATN signal, the Target changes to the Message Out phase and receives a message from the
Initiator.
If the first message received is a Wide Data Transfer Request message, the Target establishes the new data transfer mode. The
Byte Value Description
0 01H Extended message
1 02H Extended message length
2 03H WIDE DATA TRANSFER REQUEST code
3 E Transfer width exponent
Initiator's
request
Target’s
response
Target Data Transfer
Width
Ei = 00h Et = 00h 8 Bit Data Transfers
Ei > 00h Et = 01h 16 Bit Data Transfers