Sony DDS-4 Product Description Manual page 85

6. COMMAND SPECIFICATION
Buffered Mode:
Buffered Mode is the mechanism by which the drive implements Immediate Reporting on WRITE commands.
If the field is zero, then the drive does not report a GOOD status on WRITE commands until the data blocks are
actually written to tape.
If the Buffered Mode field is one, then the drive reports GOOD status on WRITE commands as soon as the data
block has been transferred to the buffer. This is the default configuration for the drive.
If Buffered Mode is not used, the drive will suffer a significant degradation in performance with respect to capacity
as each record will be written as a partial group. Partial groups are not appended to automatically, but are left on the
tape.
Speed:
The drive only supports one speed, the default speed. Because of this, this field must be set to zero. Any other value
will cause a CHECK CONDITION status with an IL LEGAL REQUEST sense key is returned.
Block Descriptor Length:
This specifies the length in bytes of all the block descriptors. Since the drive only allows one block descriptor, this
value must be eight. Any other value will cause a CHECK CONDITION status with an ILLEGAL REQUEST
sense key to be returned.
Note: The block descriptor specifies the media characteristics for the DDS drive. The block descriptor contains the
density code, number of blocks and block length fields.
Density Code:
The supported values for the density code field are defined in the following table.
Code Value
00h
13h
24h
25h
26h
7Fh
Note: 00h - Default: The use of the word "Default" is SCSI specific. It instructs the drive to use its default or only
density. Therefore the drive uses its only density of 13h. 13h is the value that has been allocated for use by DDS
devices by the ANSI SCSI Committee (X3T9.2).
6 - 34 SONY SDT-10000/SDT-11000 DDS Tape Drive
Density
Default Format
Sony/Hewlett Packard DDS1 Format
Sony/Hewlett Packard DDS2 Format
Sony/Hewlett Packard DDS3 Format
Sony/Hewlett Packard DDS4 Format
No change from previous density (No-Op)
Table 6-25: Sequential-Access Density Codes
MODE SELECT