Freecom FC TapeWare AIT-450i, Руководство пользователя

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6.Command Specification SPACE
SONY AIT-1 Turbo drive SDX-450V series Ver.1.0 6-96
6.26.
SPACE 11h
Bit
Byte
7 6 5 4 3 2 1 0
0 Operation Code (11h)
1 Logical Unit Number Reserved Code
2 (MSB)
3 Count
4 (LSB)
5 Unused (00b) Reserved Flag Link
SPACE provides a variety of positioning functions that are determined by the Code and Count fields in the Command
Descriptor Block. Both forward (toward EOM/P) and reverse (toward BOM/P) positioning are provided.
Code : The supported values are:
Table 6-76: SPACE codes
Code Description
000b
001b
011b
100b Blocks
File-marks
End-Of-Data
Set-marks
Note : The drive will reject a SPACE Set-mark command if it has not configured through MODE SELECT to report
Set-marks. The drive will return a CHECK CONDITION status with the Sense data set to ILLEGAL REQUEST. In
this command description the word “mark” is used to mean File-mark or Set-mark. Only where their responses differ
shall File-mark and Set-mark be referred explicitly.
Count : When spacing over blocks or marks, the Count field is interpreted as follows:
A positive value N causes forward movement over N blocks or marks. The tape is logically positioned after the Nth
block (or mark) on the EOM/P side.
A ZERO value causes no change in the logical position.
A negative value -N (2’s complement notation) causes reverse movement over N blocks or marks. The tape is
logically positioned on the BOM /P side of the Nth block (or mark).
When spacing to EOD, the Count field is ignored. Forward movement occurs until the drive encounters EOD. The
position is such that a subsequent WRITE command would append data after the last entity that has been written to
tape before EOD.
When executing a SPACE, the drive implements the following hierarchy: Blocks (lowest), File-marks, Set-marks,
EOD, BOM/P or EOM/P (highest)
Therefore, SPACE N blocks will halt with GOOD status after the Nth block, or with CHECK CONDITION status on
any occurrence of File-mark, Set-mark, EOD, BOM/P or EOM/P. A SPACE N File-marks will halt on the Nth
File-mark or on any occurrence of Set-mark, EOD, BOM/P or EOM/P, and so on. Within the Sense data, the fields
will be set as described on the following table.