4.1 Control/Sense Commands

4.1.3 READ CAPACITY (25)

Byte

Bit

7

6

5

4

3

2

1

0

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

X'25'

 

 

 

1

 

0

0

0

0

0

0

0

0

2

 

 

 

 

Logical Block Address (MSB)

 

 

3

 

 

 

 

Logical Block Address

 

 

 

4

 

 

 

 

Logical Block Address

 

 

 

5

 

 

 

 

Logical Block Address (LSB)

 

 

6

 

0

0

0

0

0

0

0

0

7

 

0

0

0

0

0

0

0

0

8

 

0

0

0

0

0

0

0

PMI

9

 

0

0

0

0

0

0

0

0

This command transfers information related to the disk drive's capacity and the data block size to the INIT.

When bit 0 "PMI (partial medium indicator)" of CDB byte 8 is "0," the logical block address and block length (byte length) of the final data block which is accessible in the disk drive (user space) are transferred to the INIT. At this time, the "Logical Block address" field in the CDB must specify zero.

When the "PMI" bit is "1," the logical block address and block length (byte length) of data blocks which satisfy either of the following conditions is transferred to the INIT.

The data block on the track where the specified block exists, which is just before the block where the first alternate sector processing (not including defective block sector slip processing) is implemented. However, when alternate sector processing is being implemented in the specified block, the data block specified in the CDB.

When no alternate sector processed data block exists in the track where the specified block exists, the last data block in that track.

By using this command with the "PMI" bit specified as "1", the INIT can search for usable data space continuously without being interrupted by data transfers for alternate sector processing or switching of cylinders.

The format of the data transferred to the INIT by this command is shown in Table 4.11.

C141-C013

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Fujitsu MBC2036RC, MBC2073RC, MBA3300RC, MBA3147RC, MBA3073RC specifications Read Capacity