4-3.29 Space Command 11H; 4-3.29.1 Space Cdb Description; Table 4-125. Space Field Description; Table 4-126. Code Field Bits - Fujitsu M2488 Product Manual

M2488 PRODUCT GUIDE
4-3.29 SPACE command 11h
The Space command changes the logical unit position relative to the current position. The Code and
Count fields determine how this relative positioning is to be performed. Before the position change
occurs, any buffered write data and filemarks are written to the tape.
4-3.29.1 SPACE CDB Description
SPACE is a six-byte command. The bytes are shown below and described in Table 4-125. Com-
mon fields are described in paragraph 4-3.1 on page 4-4.:
7
BYTES
0 0
1
2 MSB
3
4
5
Note: Changeable fields in the CDB are shaded.
BYTE BIT VALUE
0 0-7
1 0-2
2-4
CODE FIELD TYPE
000b Space N Blocks
001b Space N Filemarks
010b Space to N Sequential
Filemarks
011b Space to End-of-Data
April 1997
6 5 4
0 0 1
LUN
Count Field
Reserved

Table 4-125. SPACE Field Description

11h Operation code.
The Code Field bits are described in Table 4-126.
The 3 byte Count Field is a 24-bit signed number (two's complement). When the
count field is 0, no position change occurs and buffered write data will not neces-
sarily be written to tape. To force buffered write data to tape, issue a WRITE
FILEMARK command with a count of 0.

Table 4-126. Code Field Bits

If the Count field is positive then space forward N blocks; N = Count. If the
Count field is negative then space backward N blocks; N = -Count.
If the Count field is positive then position forward to the End-of-Tape side of
the Nth filemark encountered; N = Count. If the Count field is negative then
position backward to the Beginning-of-Tape side of the Nth filemark
encountered; N = -Count.
If the Count field is positive then position forward to the End-of-Tape side of
the next occurrence of N consecutive filemarks; N = Count. If the Count
field is negative then position backward to the Beginning-of-Tape side of the
next occurrence of N consecutive filemarks; N = -Count.
The count field is ignored. Upon successful completion, the tape is posi-
tioned such that a subsequent write command will append data after the last
recorded block. If the tape is in 18-track format, end-of-data is defined as
two sequential filemarks.
CG00000-011503 REV. A
TAPE UNIT SCSI COMMANDS
BITS
3 2
0 0
Reserved
DESCRIPTION
DESCRIPTION
1 0
0 1
Code Field
LSB
Flag Link
4-135