Data Format 3-12 C141-E237 If above errors are detected during FORMAT UNIT command, the HDDs allocate the alternate
block(s) to the defective data blocks. Reassign procedure itself is the same as one in REASSIGN
BLOCKS command.
*1 Certification is permitted when DCRT flag is cleared (DCRT flag=0) in FORMAT UNIT
command.
The HDDs check all initialized logical data blocks by reading them out after the above alternate
block allocation is made to initialize (format) the disk.
(2) Alternate block allocation by REASSIGN BLOCKS command
When the REASSIGN BLOCKS command is specified, the alternate block is allocated to the
defective logical data block specified by the initiator by means of alternate sector treatment. The
alternate block is allocated to unused spare se ctors in the alternate cylinder.
Figure 3.8 is examples of the alternate block allocation by the REASSIGN BLOCKS command.
: Unused spare sector
Example Reassign: Block 16
: Defective sector
: n represents a logical data block number
Figure 3.8 Alternate block allocation by REASSIGN BLOCKS command