IBM DCAS-32160 - Ultrastar 2.1 GB Hard Drive, Specifications

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Target
Initiator Data Transfer
Request Width
ÄÄÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
Ei = 00h 8 Bit Data Transfers
Ei = 01h 16 Bit Data Transfers
Ei > 01h Send Message Reject (8 bit Data Transfer)
Figure 129. Target Request to Initiator
Note: If the corresponding transfer width exponent received from the Initiator indicates a data transfer width
that is greater than 16 bits (E > 01h) the Target sends a Message Reject message to the initiator to indicate
8 bit data transfer mode.
If the first message received from the Initiator is either a Message Parity Error or a Message Reject message,
the Target goes to 8 bit data transfer mode. For the Message Parity Error case, the wide data transfer nego-
tiation is restarted if the Target successfully retransmits the Wide Data Transfer Request message to the Initi-
ator.
If the first message received from the Initiator is any other message, the Target goes to 8 bit data transfer
mode. The Target assumes that the Initiator does not support wide data transfer and does not attempt to
renegotiate with this Initiator.
The implied agreement for wide data transfer operation is not considered to exist by the Target until the
Target leaves the Message Out phase, implying that no parity error was detected.
If the Target detects a
parity error while attempting to receive the message from the Initiator, the Target goes to 8 bit data transfer
mode. The Target will attempt to resume the wide data transfer negotiation by retrying the Message Out
phase.
Note: If during the Message In phase of negotiations, either Target or Initiator started, A T N is asserted
prior to transmission of the last byte of the message and the message is not Message Parity or Message
Reject, the Target goes to 8 bit data transfer mode.
9.1.4 SAVE DATA POINTER (02)
This message is sent from the file to direct the initiator to copy the active data pointer to the saved data
pointer.
The SAVE DATA P O I N T E R message is only sent if the initiator has previously indicated the
ability to accommodate disconnection and reconnection via the I D E N T I F Y message .
The file will send the SAVE DATA P O I N T E R message to the initiator prior to sending a DISCONNECT
message to the initiator if a data phase has occurred and another data phase is required to successfully com-
plete the command.
9.1.5 RESTORE POINTERS (03)
This message is sent from the file to direct an initiator to copy the most recently saved pointers to the corre-
sponding command, data, and status pointers.
Command and status pointers should be restored to the
beginning of the present command and status areas. The data pointer should be restored to the value at the
beginning of the data area in the absence of a SAVE DATA P O I N T E R message or to the value at the point
at which the last SAVE DATA P O I N T E R message occurred. Also see 9.4, “SCSI Bus Related Error Han-
dling Protocol” on page 176.
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O E M Spec. of DCAS-34330/32160