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2.8.2
Logical block addressing
The IDD uses logical data block addressing which is not dependent on the disk drive's
physical structure as the method of data access on the disk medium.
correspondence between each physical sector and each logical data clock address during
formatting. Access to the data on the disk medium is performed in logical data block units
and the INIT specifies the logical data block address that is its object during access.
In logical data block addressing, specifying of a data block address is a function which
specifies 2 continuous binary numbers for each drive. Furthermore, the INIT can know the
logical data block address range in the user space where specification is possible using the
READ CAPACITY command.
(1)
User space logical block addresses
The top data block in the user space is made logical data block address "0," then continuous
logical data block addresses are allocated to each data block until the last data block in the user
space.
The IDD makes cylinder 0, track 0 sector 0 the top logical data block, and allocates
subsequent logical data blocks in the order described below to addresses in ascending order.
1) Within the same track, logical data blocks are allocated to sector numbers in ascending
order.
2) Within the same cylinder, excluding the final track, succeeding logical data blocks are
allocated to the sectors in each track according to 1) in the ascending order of track
numbers.
3) On the last track inside the same cylinder, succeeding logical data blocks are allocated to
sectors except for spare sectors according to 1).
4) After all the allocation in 1) to 3) is completed within the same cylinder, succeeding
logical data blocks are allocated to the next cylinder beginning with track 0, according to
1) to 3), and so on to each cylinder number in ascending order until the last cylinder
(cylinder p-q in Figure 2.10) in the user space, with the exception of alternate cylinders.
(2)
Alternate area
The alternate area in user space (spare sectors within each cylinder and alternate cylinders) are
excluded from the abovementioned logical data block addresses. Access to allocated sectors
as alternate blocks within the alternate area is performed automatically by the IDD's defect
management (sector slip processing and alternate block processing), so it is not particularly
necessary for the user to access the alternate area. Also, data blocks in the alternate area
cannot be clearly specified and accessed directly.
C141-E054-02EN
The IDD makes
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