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5-72 Quantum DLT 7000 Tape System
MODE SELECT (6) / (10) Command (15h) / (55h) (continued)
Table 5–38 MODE SELECT Mode Parameter Block Descriptor - Field Descriptions
(continued)
Field Name Description
Number of
Blocks
This MODE SENSE field is sent = 0, indicating that all of the remaining logical blocks
on the tape will have the medium characteristics specified by the block descriptor.
Block Length This field specifies the length, in bytes, of each logical block transferred over the
SCSI bus. A block length of 0 indicates that the length is variable (specified in the I/O
command). Any value other than 0 indicates the number of bytes per block to use
for READ, WRITE, and VERIFY commands that specify a “fixed” bit of 1 (i.e., fixed
block mode) which also causes the transfer length in the command descriptor
block to be defined as a block count. If fixed bit is not equal to 1, this field is
ignored.
5.9.1.3 Mode Page Descriptors
Following the MODE SELECT command’s Mode Parameter Block Descriptor are
the MODE SELECT pages, each of which sets a different device parameter. Each
mode page has a 2-byte header that identifies the page code and indicates the
number of bytes in that page.
Bit
Byte
7 6 5 4 3 2 1 0
0 PS (0) 0 Page Code
1 Additional Page Length
2 - n Page-Defined or Vendor Unique Parameter List
Figure 5–36 MODE SELECT Page Descriptor - Data Format