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SCSI Commands

Quantum DLT 8000 Tape System 5-87

MODE SELECT Command (6) / (10) (15h) / (55h) (continued)

Table 5–43 Data Compression Page Descriptor — Field Descriptions

Field Name Description

Page Code The Page Code identifies the type of MODE SELECT page being

transferred. A value of 0Fh identifies this as the Data Compression

page.

Page Length 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.

DCE 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.

DCC Data Compression Capable. This bit is used by the MODE SENSE

command to indicate that the tape drive supports data compression.

DDE 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.

RED 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.

Compression Algorithm 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.

Decompression Algorithm 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.

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Quantum DLT 8000 Manual Página 231