Wide Mode Transfer (16-Bit Scsi) - Fujitsu MBA3073 SERIES Technical Manual

The TARG shall only respond to an iuCRC error after all the data in an information unit has been
received.
If the nexus has been fully identified (i.e., an I_T_L_Q nexus has been established) and the TARG
detects an iuCRC error in any SPI data information unit, SPI data stream information unit, or last
command SPI command information unit it receives while in the DT DATA OUT phase the
TARG shall switch to a DT DATA IN phase and send a SPI L_Q/SPI status information unit pair
to the INIT, before sending any other SPI L_Q information unit. The status information shall
indicate a CHECK CONDITION status and a sense key set to ABORTED COMMAND and the
additional sense code set to INFORMATION UNIT iuCRC ERROR DETECTED for the task
associated with the iuCRC error.
If the TARG detects an iuCRC error on an iuCRC interval that is not at the end of a SPI information
unit the TARG shall not respond to the error until all the bytes of the SPI information unit in which
the error occurred have been transferred. The TARG may discard the transmitted information.
If the TARG is receiving a SPI L_Q information unit and the TARG detects an iuCRC error (i.e.,
the nexus identification fails) the TARG shall cause an unexpected bus free by generating a BUS
FREE phase (see 10.3).
If a TARG receives a SPI L_Q information unit with a type code that is not defined in Table 1.25 that
TARG shall transfer all the bytes indicated in the DATA LENGTH field and iuCRC INTERVAL
field and shall discard the transmitted information for the information unit that follows the SPI L_Q
information unit. After transferring all the bytes the TARG shall change to a DT DATA IN phase and
transmit a SPI status information unit with a RSPVALID bit of one and the packetized failure code
set to INVALID TYPE CODE RECEIVED IN SPI L_Q INFORMATION UNIT.
If a TARG receives a SPI L_Q information unit with an illegal data length the TARG shall
transfer all the bytes indicated by the data length and iuCRC interval and shall discard the
transmitted information. After transferring all the bytes the TARG shall change to a DT DATA IN
phase and transmit a SPI status information unit with a RSPVALID bit of one and the packetized
failure code set to ILLEGAL REQUEST RECEIVED IN SPI L_Q INFORMATION UNIT.

1.6.5.4 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 HDD 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
message is received, data is transferred using 8-bit mode until the mode is switched to "16-bit
mode" by exchanging the WIDE DATA TRANSFER REQUEST message.
1-25 C141-C007