Ciprico Rimfire 3880 Manuel D’Utilisation
User’s Guide
21020285 D
Chapter 8 Details of Usage
Target Mode Usage and SCSI Protocol Handling
Page 8 - 13
Wide Data
Transfer
Requests
When Wide Data Transfers are enabled, (WID bit set to 1, of the Unit Flags
byte of either the Unit Options, 08H, or Extended Unit Options, 18H,
commands), the adapter will send a Wide Data Transfer Request (WDTR)
message whenever it determines that the data transfer agreement is in an
indeterminate state. The adapter will initiate the exchange of WDTR messages
immediately before starting the data transfer phase. The adapter will also send
a WDTR message in response to a WDTR message received from the initiator.
byte of either the Unit Options, 08H, or Extended Unit Options, 18H,
commands), the adapter will send a Wide Data Transfer Request (WDTR)
message whenever it determines that the data transfer agreement is in an
indeterminate state. The adapter will initiate the exchange of WDTR messages
immediately before starting the data transfer phase. The adapter will also send
a WDTR message in response to a WDTR message received from the initiator.
Unexpected
Messages
Received from
the Initiator
If an abort, bus device reset, or related message is received (during Target Mode
command processing), it will be passed to the host as an unexpected event. The
adapter will not disconnect from the SCSI bus until instructed to do so by the
host. After receiving the message, the host issues the necessary adapter
commands (Abort command) followed by a Target Mode Response command
containing a Bus Free instruction to release the SCSI bus.
command processing), it will be passed to the host as an unexpected event. The
adapter will not disconnect from the SCSI bus until instructed to do so by the
host. After receiving the message, the host issues the necessary adapter
commands (Abort command) followed by a Target Mode Response command
containing a Bus Free instruction to release the SCSI bus.
Automatic
Adapter
Responses
The adapter will automatically respond to several events without input from
the host. These events are:
the host. These events are:
•
Adapter-detected parity errors
•
A received Initiator-detected Error message
•
A received Message Parity Error message
The adapter will retry the operation in progress whenever any of these events
occur. The adapter will continue to retry the operation until the configured retry
limit is exceeded (adapter Unit Options command).
occur. The adapter will continue to retry the operation until the configured retry
limit is exceeded (adapter Unit Options command).
Once the retry limit is reached, the adapter will attempt to send a status of Check
Condition followed by a message of Command Complete. If a status byte has
been sent, a Restore Pointers message is sent. This means that when the retry
limit for a command is reached, the command can end in either of two ways:
Condition followed by a message of Command Complete. If a status byte has
been sent, a Restore Pointers message is sent. This means that when the retry
limit for a command is reached, the command can end in either of two ways:
•
A status byte followed by a message
•
A message followed by a status byte followed by a message
If the status/message cannot be sent without error, the adapter will go to the
Bus Free phase (an unexpected disconnect). The Host will be notified of this
occurrence and should prepare sense data for the initiator (Contingent
Allegiance Condition).
Bus Free phase (an unexpected disconnect). The Host will be notified of this
occurrence and should prepare sense data for the initiator (Contingent
Allegiance Condition).
The adapter will also automatically respond to the initiator’s data transfer
negotiation requests:
negotiation requests:
•
Synchronous Data Transfer Request (SDTR) message.
•
Wide Data Transfer Request (WDTR) message.