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CHAPTER 2 Command Processing
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
In this chapter, the basic theory and specifications concerning IDD command
processing functions are described.
2.1 Command Format
Input/Output commands from the INIT (Initiator) to the IDD are executed by the
CDB (Command Descriptor Block). The CDB is information which is transmitted
from the INIT to the TARG in the CMND frame. In a number of commands, other
than the CDB specifications, parameters which are necessary in executing a
command are specified in the DATA frame. Details concerning these commands
are described in the specifications for individual commands in Chapter 4.
The CDB used by the IDD has 4 formats, one with a length of 6, 10, 12 bytes and
the other with a length of 16 bytes. The basic format of each respective CDB is
shown in Tables 2.1, 2.2 and 2.3.
C141-C009
Command Format
Status Byte
Command Queuing Function
UNIT ATTENTION Condition
Sense Data Hold State
Power Condition
LED Display
Command Processing Exceptions
Data Block Addressing
The IDD operates as the target (TARG). In the explanations given
in this chapter, the IDD is labeled "TARG", except in cases where a
particularly clear distinction is necessary.
2-1
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