Specifications

Data Structures
1.16 SCSI Connection Descriptor Table (SCDT)
Table 1–18 (Cont.) Contents of SCSI Connection Descriptor Table
Field Name Contents
SCDT$L_DMA_TIMEOUT* Timeout value (in seconds) for a target to change the SCSI bus phase or
complete a data transfer. The SCSI port driver initially writes this field
according to information the SCSI class driver supplies to the SPI$SET_
CONNECTION_CHAR macro.
SCDT$L_DISCON_
TIMEOUT*
Disconnect timeout. Default timeout value (in seconds) for a target to
reselect the initiator to proceed with a disconnected I/O transfer. The SCSI
port driver initially writes this field according to information the SCSI
class driver supplies to the SPI$SET_CONNECTION_CHAR macro.
SCDT$L_SEL_CALLBACK* Address of class driver’s asynchronous event notification callback routine.
SCDT$L_SEL_CONTEXT Context for class driver callback.
SCDT$L_PORT_QFL Forward queue header link in managing the incoming port queue. As each
I/O is sent to the device, it is removed from the port queue and placed on
the in-device queue (SPDT$L_DEV_QBL).
SCDT$L_PORT_QBL Backward (tail) queue header link in managing the incoming port queue.
SCDT$L_DEV_QFL Forward queue header link in managing the in-device queue of I/O requests
that were sent to the device.
SCDT$L_DEV_QBL Backward (tail) queue link in managing the in-device port queue.
SCDT$L_QUEUE_FLAGS Port queue flags for queue management are as follows:
SCDT$V_CMDQ Indicates this connection supports command
queuing.
SCDT$V_FLUSHQ Indicates this connection is to flush on error.
SCDT$V_SCSI_2 Indicates the device conforms to SCSI-2.
SCDT$V_QUEUE_
WAIT
Indicates the port queue is currently waiting for
a command to complete in the device. The I/O
causing the wait is identified in the SCDT$W_
WAIT_TAG field. When this I/O completes,
the SCDT$V_QUEUE_WAIT bit is cleared
unblocking the queue.
SCDT$V_QUEUE_
FROZEN
Indicates a queued command has terminated
with a CHECK_CONDITION SCSI status.
Used by the port driver to know when the port
is waiting for the class driver to complete its
error recovery. Cleared by the SPI$RELEASE_
QUEUE call. Any I/O received while this bit is
set is immediately returned to the class driver
with failure status. This bit is also set by the
SPI$FREEZE_QUEUE call.
SCDT$V_FLUSHING_
QUEUE
Indicates the port is flushing the device and
port queues. I/O received while this bit is set
is immediately returned to the class driver
with failure status. Cleared by a count 0 in
the SCDT$W_DEV_IO_COUNT and SCDT$W_
PORT_IO_COUNT fields. This bit is also set by
the SPI$FLUSH_QUEUE call.
SCDT$V_QUEUE_
FULL
Queue full status detected.
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