Table of Contents
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Command Specifications
a.
Header
−
−
−
b.
Block descriptor
The logical attributes of the data format on the disk media are described in the
8-byte long "Block descriptor."
−
−
4-22
Media type
X '00' (default type) must be specified in this field.
Byte 2
Bits 7 and 4 of this field have meaning only in the header transferred to
the INIT by the MODE SENSE and MODE SENSE EXTENDED
commands. The values specified in these bits are disregarded in the
MODE SELECT and MODE SELECT EXTENDED commands. "0"
must always be specified by the INIT in the other bit positions.
Block descriptor length
This field indicates the length (block count) of the "Block descriptor"
which follows the header (not including the length of the "Page
descriptor"). It is possible to define only 1 "Block descriptor" to the
IDD, and either X '00' or X '08' must be specified in this field. When X
'00' is specified in this field, it indicates that the "Block descriptor" is not
included in the parameter list transferred from the INIT and the "Page
descriptor" follows immediately after the "Header."
Data block count
This field specifies the total number of logical data blocks (the block
length is specified in "Data block length") allocated in the user space on
the disk media. The maximum logical block address is a value with 1
subtracted from the value in this field.
If only the "Block descriptor" in this command is changed accessible
data block count can be limited without formatting if "Data block count"
value is within a "Cylinder count" value of page 4.
If zero is specified for the "Data block count," or when the block
descriptor is not specified, the IDD retains its current capacity, if the
block size or alternate sector count has not changed. If the "Data block
count" is set to zero and the Data block size or alternate sector count has
changed, the IDD shall set to its maximum capacity when new block size
or alternate sector count to be effect.
Data block length
This field specifies the byte length of a logical data block on the disk
media.
The logical data block length and physical data block length are the same
in the IDD. The data block length can be specified at 512 to 528 bytes
(4-byte boundary).
C141-C009
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