Hitachi HUS151414VL3600, Specifications

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Hitachi Ultrastar 15K147 SCSI Hard Disk Drive Specification
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19.3 Attention condition
The attention condition allows an Initiator to inform the drive that a MESSAGE OUT phase is desired. The Initiator may cre-
ate the attention condition by asserting the ATN signal at any time except during the ARBITRATION or BUS FREE phases.
The Initiator must create the attention condition by asserting the ATN signal at least two deskew delays before releasing ACK
for the last byte transferred in a bus phase to guarantee that the attention condition will be honored before transition to a new
bus phase. This will guarantee a predictable drive response to a message received during the MESSAGE OUT phase for this
attention condition. If the ATN signal is asserted later, it may be honored in the current bus phase or the next bus phase and
then may not result in the expected action.
After the Initiator asserts the ATN signal, the drive will respond with the MESSAGE OUT phase as follows:
Current phase Response
COMMAND MESSAGE OUT phase will occur after part or all of the Command Descriptor Block has been transferred to
the drive. The Initiator must continue REQ/ACK handshakes during the COMMAND phase until the drive
enters the MESSAGE OUT phase.
DATA The Message Out phase will occur after part or all of the data bytes have been transferred and not necessarily
on a logical block boundary. The Initiator must continue REQ/ACK handshakes (asynchronous transfer)
until it detects the phase change.
Note: In synchronous transfer the Initiator must continue sending ACK pulses to reach an offset of zero.
STATUS The Message Out phase will occur after the REQ/ACK handshake of the status byte has been completed.
MESSAGE IN The Message Out phase will occur before the drive sends another message.
SELECTION If ATN occurs during a Selection phase and before the Initiator releases the BSY signal, the Message Out
phase will occur immediately after that Selection phase.
RESELECTION The MESSAGE OUT phase will occur after the drive has sent its IDENTIFY message for that RESELEC-
TION phase. (The drive first tries to complete the reselection.)
The Initiator must keep the ATN signal asserted if more than one message byte is to be transferred during the MESSAGE Out
phase. The drive will process each message byte (multiple bytes for an extended message) prior to receiving the next message
from the Initiator. The drive will continue to handshake and process byte(s) in the MESSAGE OUT phase until ATN goes false
unless one of the following conditions occurs:
1. The drive receives an illegal or inappropriate message and goes to the MESSAGE IN phase to send a MESSAGE
REJECT message.
2. The drive detects a catastrophic error condition and goes to the BUS FREE phase.