Seagate STD124000N Product Manual page 9

Product Manual
Subcode Location ........................................................................ 49
DDS-3 Track Geometry ............................................................... 50
Recorded Patterns....................................................................... 51
Format of a Track ........................................................................ 51
Positioning Accuracy.................................................................... 52
Timing Tracking ........................................................................... 52
Tape Layouts in the DDS-3 Standard ................................................. 53
Layout of a Single Data Space Tape (Single Partition)........................ 53
Device Area ................................................................................. 54
Reference Area............................................................................ 54
System Area................................................................................ 55
Data Area .................................................................................... 55
Appending to Tape....................................................................... 55
EOD Area .................................................................................... 57
Early Warning Point (EWP).......................................................... 57
Initialization.................................................................................. 57
Layout of a Partitioned Tape .............................................................. 58
Partition 1 .................................................................................... 59
Partition 0 .................................................................................... 59
Initialization of Partitioned Tapes.................................................. 59
Housekeeping Frames ....................................................................... 60
DDS-3 Recording Format Standard-Further Reference .................... 60
7 Data Compression .......................................................... 61
Introduction ........................................................................................ 61
Data Compression-General.............................................................. 61
Data Compression Considerations ............................................... 62
Hardware Compression ............................................................... 63
Data Integrity ............................................................................... 63
DCLZ Algorithm ................................................................................. 64
DCLZ Algorithm ........................................................................... 64
Simplified Compression Operation ............................................... 64
Dictionary .................................................................................... 65
Simplified Decompression Operation............................................ 66
SCSI/Data-Compression Chip ............................................................ 68
Overview ..................................................................................... 68
Features ...................................................................................... 68
8 Theory of Operations...................................................... 71
Overview............................................................................................ 71
The STD124000N Drive............................................................... 72
Motors and Control Circuits.......................................................... 73
SCSI Controller............................................................................ 74
Helical Scan Recording-Four-Head Design ................................ 75
Motors and Control Circuits ................................................................ 76
Read and Write LSI ..................................................................... 77
Timing Tracking Circuitry ............................................................. 77
SCSI Controller............................................................................ 77
Contents
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