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21020285 D User’s Guide
Chapter 4 Command Operation
Page 4 - 4 The Base Parameter Block
The Base
Parameter
Block
The Parameter Block is one of the basic building blocks of the RF3880
command structures. It is designed to hold all facts relevant to a single
command.
The same Parameter Block format is used whether the command is a Pass-
through command directed to a SCSI device, or a Board-control command to
be interpreted and acted on by the adapter. (The various flags and byte values
may have different meanings in each case though.)
All Board-control commands are described in detail in Chapter 7. More
information about how the RF3880 implements SCSI commands can be found
in Chapter 5. See a SCSI specification and vendor-supplied peripheral
documentation for details about particular SCSI commands.
Parameter
Block Format
The Parameter Block format for all Pass-through and also adapter Board-
control commands is illustrated below:
A brief description of each of the fields follows:
Command Identifier
When setting up a command structure, you use this field to distinguish a
command in order to associate it with a returned Status Block. The value is a
double-word and must be unique; the Command Identifier for each currently
executing command should be different. Any unique four-byte value will work.
You could, for example, use the command address or a Parameter Block Index
pointer as the Command Identifier. Both Pass-through commands and adapter
Board-control commands use this field for proper identification of status to be
returned whether the command is issued in a Single Command structure or a
Command List.
Address
Offset
Byte Memory Address
Offset + 0 Offset + 1 Offset + 2 Offset + 3
00H Command Identifier
04H
Command Options, Addresses, and Transfer Count
Target/Adapter ID
08H
0CH
10H Command Code
Command Descriptor Block14H
18H
Table 17: Base Parameter Block