Parallel Protocol Request (01, 06, 04H); Table 175. Target Request To Initiator; Table 176. Parallel Protocol Request - Hitachi HUS151473VL3800 - Ultrastar 73.4 GB Hard Drive Specifications

drive interprets the Initiator corresponding transfer width exponent as shown in the following table.
Table 175: Target request to Initiator
Initiator request
Ei = 00h
Ei = 01h
Ei > 01h
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. In the case of a Message Parity Error, the wide data transfer negotiation is restarted if the Target suc-
cessfully retransmits the Wide Data Transfer Request message to the Initiator.
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 Target does not consider the implied agreement for wide data transfer operation to exist until the Target leaves the Mes-
sage 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, ATN 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.

19.1.4 Parallel Protocol Request (01, 06, 04h)

Parallel Protocol Request messages are used to negotiate a synchronous data transfer agreement and a wide data transfer agree-
ment and to set the protocol options between two SCSI devices.
Table 176: Parallel Protocol Request
Byte
7
0
1
2
3
4
5
6
PCOMP_EN RTI
7
PARALLEL PROTOCOL REQUEST messages are used to negotiate a synchronous data transfer agreement and a wide data
Target Data Transfer Width
8 bit data transfers
16 bit data transfers
Send Message Reject (8 bit data transfer)
6 5 4
Extended Message = 01h
Extended Message Length = 06h
Parallel Protocol Request = 04h
Transfer Period Factor
Reserved = 00h
REQ/ACK Offset
Transfer Width Exponent
RD_STRM WR_FLOW HOLD_MCS QAS_REQ DT_REQ
Hitachi Ultrastar 15K147 SCSI Hard Disk Drive Specification
Bit
3 2
217
1 0
IU_REQ