Seagate Ultra 320 - Manual (Page 140)

126 Parallel SCSI Interface Product Manual, Rev. A
tion unit the P_CRCA signal was asserted and a SCSI initiator port detects a REQ transition after receiving the
last iuCRC for a SPI data stream information unit, that SCSI initiator shall logically disconnect from the current
I_T_L_Q nexus.
If, during a sequence of SPI data stream information units a SCSI initiator detects any change to the C/D, I/O,
or MSG signals after transmitting or receiving the last iuCRC for a SPI data stream information unit, that initia-
tor shall consider the current I/O process to be logically disconnected or in the case of detecting a BUS FREE
phase or a MESSAGE IN phase to be physically disconnected.
The detection of a BUS FREE phase following a SPI data stream information unit by a SCSI initiator shall be
equivalent to the initiator port receiving a DISCONNECT message.
The detection of a QAS REQUEST message following a SPI data stream information nit by a SCSI initiator
shall be equivalent to the initiator receiving a DISCONNECT message.
To end a sequence of SPI data stream information units, a SCSI initiator may request a disconnect by estab-
lishing an attention condition. The initiator shall continue to transfer or receive data, pad bytes (if any), and
iuCRCs until the target changes to the MESSAGE OUT phase.
During a sequence of SPI data stream information units the offset count is not required to go to zero at the
boundary of any SPI data stream information unit if the next SPI information unit is a SPI data stream informa-
tion unit.
Table 53: SPI status data stream information unit
[1] The Data field may contain any type of information (e.g., parameter lists, mode pages, user data).
[2] The iuCRC field shall use the algorithm defined in Subsection 11.3 of ANSI SCSI Parallel Interface (SPI-
5). If the iuCRC Interval field of the SPI L_Q information unit contains a value greater than zero and less
than the data length, then there is an iuCRC field at each iuCRC interval in addition to the iuCRC shown in
this table. These additional iuCRC fields are not shown in this table.
Bit
Byte
7 6 5 4 3 2 1 0
0 MSB
DATA [1]
n
LSB
n+1 MSB
iuCRC [2]
n+2
n+3
n+4 LSB