Quantum DLT 8000 Product Manual page 231

MODE SELECT Command (6) / (10) (15h) / (55h) (continued)
Table 5–43 Data Compression Page Descriptor — Field Descriptions
Field Name
Page Code
Page Length
DCE
DCC
DDE
RED
Compression Algorithm
Decompression Algorithm
Description
The Page Code identifies the type of MODE SELECT page being
transferred. A value of 0Fh identifies this as the Data Compression
page.
The Page Length field indicates the number of bytes in the Data
Compression page that follow this byte. The valid value for this byte
is 0Eh.
Data Compression Enable. This bit specifies whether the tape drive
should enable or disable data compression. When set to 1, the drive
starts in compressed format.
Data Compression Capable. This bit is used by the MODE SENSE
command to indicate that the tape drive supports data compression.
Data Decompression Enable. Must be set to 1. When the tape drive
reads compressed data from tape, it automatically decompresses the
data before sending it to the initiator. Data compression must always
be enabled.
Report Exception on Decompression. The tape drive does not report
exceptions on decompression (boundaries between compressed and
uncompressed data). The RED field must be 00h.
The Compression Algorithm field indicates which compression
algorithm the tape drive will use to process data from the initiator
when the DCE bit (byte 02, bit 7) is set to 1. The only value currently
supported for this field is 10h.
NOTE: Specifying a value other than 10h for this field causes the
tape drive to return CHECK CONDITION status, sense key set
to ILLEGAL REQUEST. However, if EEPROM parameter
EnaRepDecomp is set, the parameter in this field is ignored
and no CHECK CONDITION status is returned.
The Decompression Algorithm field indicates which decompression
algorithm the tape drive will use when decompressing data on the
tape. The only value currently supported is 10h.
NOTE: Specifying a value other than 10h for this field causes the
tape drive to return CHECK CONDITION status, sense key set
to ILLEGAL REQUEST.
Quantum DLT 8000 Tape System
SCSI Commands
5-87