Seagate Ultra 320 - Manual (Page 132)

118 Parallel SCSI Interface Product Manual, Rev. A
[1] See Table 49 for the format of the SPI L_Q information unit.
[2] See Table 54 for the format of the SPI Status information unit.
[3] See Figure 16.
Figure 18. SPI information unit sequence during status transfers
6.2 SPI information units
6.2.1 SPI command information unit
The SPI command information unit (see Table 46) transfers CDBs, task attributes, and task management
requests to be performed by a device server.
a SCSI initiator port shall consider a BUS FREE phase after the transfer of a SPI command information unit to
be equivalent to receiving a DISCONNECT message.
If a SCSI target port does not have the resources to accept a SPI command information unit and the Task Man-
agement Flags
field equals 00h the target shall transfer all the bytes of the current SPI command information
unit but need not hold the transmitted information. After transferring all the SPI command information unit bytes
the target shall change to a DT DATA IN phase and transmit a SPI status information unit with the status
defined in the SCSI Architecture Model-4 standard (SAM-4) for this condition. If the initiator has more com-
mands to send the target, the initiator shall wait at least until the next selection before those remaining com-
mands may be sent.
SPI L_Q
(always Targ to Init)
(logical reconnect)
DT DATA OUT
(from SPI DATA
or SPI COMMAND)
DT DATA IN
RESELECTION
DT DATA IN
(from SPI DATA)
SPI STATUS
(always Targ to Init)
DT DATA IN
(to SPI L_Q/DATA [3])
MESSAGE
OUT
MESSAGE
IN
(to QAS)
BUS FREE
(physical
disconnect)
(logical disconnect)
Attention
Condition
(data pointer
restored)
[1]
[2]
Data
Length
= 0