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SCSI Commands

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

1 2 ... 171 172 173 174 175 176 177 178 179 180 181 ... 311 312

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