Specifications
ATAPI For Streaming Tape QIC-157 Rev B
94
6.8.13. SPACE Command
The SPACE command is used to position to a relative filemark or to end of data depending on the
Count and Code. Both forward and reverse filemark positioning are provided. If the Device does not
support the reverse direction, then a SPACE command in the reverse direction shall be terminated
with a “Check Condition” and the Sense Key shall be set to ILLEGAL REQUEST.
Table 6-71 Space Command
Bit
Byte
7 6 5 4 3 2 1 0
0 Operation code (11h)
1 Reserved Code
2 (MSB)
3 Count
4 (LSB)
5 Reserved
6 Reserved
7 Reserved
8 Reserved
9 Reserved
10 Reserved
11 Reserved
Table 6-72 Space Code
Code Description
000b Reserved
001b Filemarks
010b Reserved
011b End of Data
100b-111b Reserved
When spacing over filemarks, the Count field specifies the number of filemarks to be spaced over in
the current partition. A positive value N in the Count field shall cause forward positioning (toward
end-of-partition) over N filemarks ending on the end-of-partition side of the last filemark. A zero
value in the Count field shall cause no change of logical position. A negative value -N (two's
complement notation) in the Count field shall cause reverse positioning (toward beginning-of-
partition) over N filemarks ending on the beginning-of-partition side of the last filemark.
Implementor's Note: Reverse movement is intended for small changes in position. Some Devices may
not support space reverse.
If end-of-data is encountered while spacing over filemarks, “Check Condition” status shall be
returned, the Sense Key shall be set to BLANK CHECK, and the Valid bit shall be set to one in the
sense data. Additionally, the EOM bit shall be set to one if end-of-data is encountered at or after
early-warning. The Information field shall be set to the difference (residue) of the requested count
minus the actual number of filemarks spaced over.
If the end-of-partition is encountered while spacing forward over filemarks, “Check Condition”
status shall be returned, the Sense Key shall be set to MEDIUM ERROR, the EOM bit shall be set to
one, and the Valid bit shall be set to one. The Information field shall be set to the difference (residue)
of the requested count minus the actual number of filemarks spaced over.