CHAPTER 2 Command Processing

2.1Command Format

2.2Status Byte

2.3Command Queuing Function

2.4UNIT ATTENTION Condition

2.5Sense Data Hold State

2.6Power Condition

2.7LED Display

2.8Command Processing Exceptions

2.9Data Block Addressing

In this chapter, the basic theory and specifications concerning HDD command processing functions are described.

The HDD operates as the target (TARG). In the explanations given in this chapter, the HDD is labeled "TARG", except in cases where a particularly clear distinction is necessary.

2.1 Command Format

Input/Output commands from the INIT (Initiator) to the HDD 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 HDD 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-C013

103

Page 107
Image 107
Fujitsu MBA3300RC, MBC2036RC, MBC2073RC, MBA3147RC, MBA3073RC specifications Command Processing, Command Format