Sony SDX-800V/R manual Space 11h, Obsolete Reserved Code, Count, Space codes

SPACE 6.Command Specification

6.27.SPACE 11h

Bit	7	6	5	4		3	2	1	0
Byte
0				Operation		Code (11h)
1		Obsolete			Reserved			Code
2	(MSB)				Count
3
4									(LSB)
5					Control

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 6-98: SPACE codes
Code		Description
000b		Blocks
001b		File-marks
011b		End-Of-Data
100b		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. 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.

SONY AIT-3Ex drive SDX-800V series Ver.1.1 6-101