Quantum Instruments DLT 7000 Data Compression Page Descriptor Field Descriptions, Dcc, Dde, Red

SCSI Commands

MODE SELECT (6) / (10) Command (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	The Compression Algorithm field indicates which compression algorithm the
Algorithm	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	The Decompression Algorithm field indicates which decompression algorithm
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 7000 Tape System 5-81