Quantum DAT 24 Drive Guia do Utilizador descarregar pdf (Página 166)

Page 154 DDS-4 SCSI Interface Manual, Rev. B

SPACE (11h)

The SPACE command uses five methods to move the tape. This command moves

the position:

• Forward or backward a specified number of data blocks.

• Forward or backward a specified number of filemarks.

• Forward or backward a specified number of setmarks.

• Forward a specified number of sequential (contiguously grouped) filemarks or

setmarks.

• Forward to the end of recorded data.

If the target block or filemark is in the buffer of the drive, no tape motion results.

Otherwise, spacing is done at high search speed.

A file example is shown below.

Block 1 2 3 4 5 6 7 8 9 10 11 12 13

BOT Data Data Data Data F/M Data Data F/M Data Data F/M F/M F/M

Position 1 2 3

• When SPACE Block count is 4 from BOT, SPACE positions the tape to the end

of the 4th block (position #1).

• When SPACE Sequential filemarks count is 2 from BOT, SPACE positions the

tape to the end of the next occurrence of a double filemark (position

# 2).

• When SPACE filemarks count is 5 from BOT, SPACE positions the tape to

position #3.

SPACE Command Descriptor Block

The following table shows the layout of the Command Descriptor Block.

Byte

Bits

7 6 5 4 3 2 1 0

0 0 0 0 1 0 0 0 1

1 0 0 0 0 0 Code

2 MSB—Count

3 Count

4 Count—LSB

5 vendor unique* 0 0 0 0 Flag Link

* This vendor-unique field is reserved and must be set to zero.

1 2 ... 161 162 163 164 165 166 167 168 169 170 171 ... 180 181

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Quantum DAT 24 Drive Guia do Utilizador Página 166