Chapter 8 Details of Usage |
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Target Mode Usage and SCSI Protocol Handling | Page 8 - 17 |
Synchronous Data Transfer Request (5 bytes) - Compare the requested transfer period and the REQ /ACK offset with the limits established on the adapter. If the limits are OK, send back these same values in another SDTR message. If the limits are not OK, modify them and send another SDTR message. If the adapter does not allow synchronous data transfer, send a Message Reject message. The adapter will handle the exchange of these messages. The limits for the adapter are part of its configuration data. If less than the required five bytes are received, the adapter will send the initiator a Message Reject.
Wide Data Transfer Request (4 bytes) - Compare the requested bus width with the width established on the adapter. If they are the same, send back the same value in another WDTR message. If they are different, adopt the smaller of the two and send this value in another WDTR message. The adapter will handle the exchange of these messages. The width for the adapter is part of its configuration data. If less than the required four bytes are received, the adapter will send the initiator a Message Reject.
Unexpected Messages - These are defined as any messages not listed and described above. The adapter will send a Message Reject message.
Reserved Messages - The adapter sends a Message Reject message.
Status or Message Sequences Sent to the Initiator (by the Host)
The following descriptions include all of the status/message sequences that may be sent to the initiator by the host. Any sequence not listed in the following paragraphs is reserved by Ciprico and must not be sent to the adapter (unpredictable results will occur).
Status Byte and Command Complete Message Byte - A status byte followed by a command complete message is to be sent to the initiator. The target will go to the Bus Free phase as soon as this message is sent.
Save Data Pointer Message Byte and Disconnect Message Byte - Directs the initiator to copy the active data pointer to the saved data pointer for the I/O process. The connection is going to be broken, but a later reconnect will be required to complete the process. The target is going to the Bus Free phase as soon as this message is sent.
Status Byte and Linked Command Complete Message Byte - A status byte followed by a Linked Command Complete message is to be sent to the initiator. The target will request the next command from the initiator as soon as this message is sent.
Status byte and Linked Command Complete (with Flag) - A status byte followed by a Linked Command Complete (with Flag) message is to be sent to the initiator. The target will request the next command from the initiator as soon as this message is sent.
Message Reject - The last message sent to the host from the initiator is either inappropriate or has not been implemented. The message will be ignored. This message must be sent in a response command with no data transfer specified.
User’s Guide | 21020285 D |
