User's Manual

DLT4000 SCSI Interface
8-58 DLT4000/DLT4500/DLT4700 Cartridge Tape Subsystem
8.4.9.6 Data Compression Page (0Fh)
The Data Compression Page specifies parameters for the control of data compression.
This page allows you to turn DLT4000 drive compressed format on and off
independently of the tape's position and allows you to enable or disable decompression
of DLT4000 drive compressed data during write operations.
Bit
7 6 5 4 3 2 1 0
0 RSVD Page Code
1 Page Length
2 DCE DCC Reserved
Byte 3 DDE RED Reserved
4 (MSB)
7 Compression Algorithm (LSB)
8 (MSB)
11 Decompression Algorithm (LSB)
12 (MSB)
15 Reserved (LSB)
Figure 8-36 Data Compression Page (0Fh)
Page Code
The Page Code identifies the type of MODE SELECT page being transferred. This is
the Data Compression Page. The valid value for the Page Code is 0Fh.
Page Length
The Page Length 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)
The Data Compression Enable bit specifies whether the DLT4000 drive should enable
or disable data compression. When the DCE bit is 1, the DLT4000 drive starts in
compressed format.
DCC (Data Compression Capable)
The Data Compression Capable bit is used by the MODE SENSE command to
indicate that the DLT4000 drive supports data compression.