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User’s Guide 21020285 D
Chapter 4 Command Operation
The Base Parameter Block Page 4 - 5
Command Options, Addresses, and Transfer Count
You will use these fields of the Parameter Block to supply an address and
transfer count when a data transfer is required by the command you wish to
issue. There are also some command-modifying options available to you
depending on the command you are issuing.
Target/Adapter ID - The Target/Adapter ID byte is very important to the
command issue process. The value you supply here determines whether the
command described in the Command Descriptor Block is a Pass-through
command or an adapter Board-control command:
• If the ID = FFH, the command is a Board-control command.
• If the ID = 0-FH (0-15), the command is destined for the SCSI target or
initiator with that ID.
Command Descriptor Block
In this part of the Parameter Block you must supply details about the command
to be executed. The Command Descriptor Block will contain a SCSI command,
a Target Mode response, or an adapter Board- control command. The RF3880
Board-control commands are explained in detail in Chapter 7. You can find
more information about issuing Pass-through commands later in this chapter
and in Chapters 5 and 6. For detail about actual SCSI commands, see a SCSI
specification or your vendor-supplied peripheral documentation.
Command Code - This field will always contain a command code for either
a Pass-through or an adapter Board-control command.