C141-E039-01EN
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a. Header
•
Media Type
X '00' (default type) must be specified in this field.
•
Byte 2
Byte 7 and byte 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."
b. Block Descriptor
The logical attributes of the data format on the disk media are described in the 8 byte long
"Block descriptor."
Note:
The parameters in the "Block descriptor" are intimately related in the Format
parameters (Page 3) and the Drive parameters (Page 4). If the parameters in the
"Block descriptor" are changed, the INIT should also specify the appropriate values in
the Format parameters (Page 3) and Drive parameters (Page 4) to correct them.
If only the "Block descriptor" in this command is changed, the IDD changes the
values in the "Sector count/track," Data byte length/physical sector," "Track skew
factor" and "Cylinder skew factor," as well as the "Cylinder count" value in the drive
parameters (Page 4) in accordance with the contents specified in the "Block
descriptor," and uses the "Current" values as is for the other parameters.