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When Transfer Length is 0, the command does not carry out data transfer. It simply ends normally
without reading any data.
It is recommended that the READ (10) command is used because there is ATAPI device which
does not support the READ (12) command.
4.6.10
READ CAPACITY command
Bit
7
Byte
0
1
Logical Unit Number
2-7
8
9-11
The READ CAPACITY command transfers data on the media capacity to the host.
Table 4.80 lists the READ CAPACITY data (PMI =0) to be transferred when the PMI (Partial
Medium Indicator) bit is 0.
Bit
7
Byte
0-3
4-7
Last Block Address specifies LBA of the last accessible block.
Block Length in Bytes indicates the number of bytes per block.
When the PMI (Partial Medium Indicator) bit is 1, the data transferred depends on the type of
media used. Transfer data for each type of media is listed in Tables 4.81 and 4.82.
Table 4.81 READ CAPACITY data (PMI = 1, MO media, FROM media)
Bit
7
Byte
0-3
4-7
Table 4.79 READ CAPACITY command
6
5
4
Operation Code (25h)
Reserved
Table 4.80 READ CAPACITY data (PMI = 0)
6
5
4
Last Logical Block Address
Block Length in Bytes
6
5
4
Last Logical Block Address
Block Length in Bytes
C156-E142-02EN
3
2
Reserved
Reserved
Reserved
3
2
3
2
1
0
PMI
1
0
1
0
4 - 57
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