HP 7925D Service Manual page 14

Theory of Operation
7925
SYNC WORD
o
87
7 WORDS
POSTAMBLE
0
1 WORD 6 WORDS
CRC
CD
ECC
0
015141312
128 WORDS
DATA
0
SECTOR 0
CYLINDER
015
1 WORD
SYNC
0
15 WORDS
SECTOR 63
PREAMBLE
CD
15
ECC - ERROR CORRECTION CODE - 6 WORDS OF CHECK AND CORRECTION INFORMATION
SYNC - SYNC WORD - 100376
8
IF ECC FIELD IS VALID (BITS 15-0)
100377 8 OTHERWISE
CYLAD - CYLINDER - CYLINDER ADDRESS (BITS 15-0)
- DATA CHECKING AND ERROR CORRECTION INFORMATION
- 12 WORDS (192 BITS) OF O's
- 15 WORDS FOR SYNCHRONIZATION AND ADDRESSING
- 128 WORDS OF DATA
- S - IF "1", SPARE TRACK IN ACTIVE USE (BIT 15)
P - IF "1", PROTECTED TRACK (BIT 14)
D - IF "1", DEFECTIVE TRACK (BIT 13)
HEAD - HEAD ADDRESS (BITS 12-8)
SECTOR - SECTOR ADDRESS (BITS 7-0)
CRC - CYCLIC REDUNDANCY CHECK - 1 WORD OF CHECK INFORMATION
POSTAMBLE
SYNC FIELD
HSAD
PREAMBLE
DATA
®
o
CD
o
o
o
CD
®
o
REF 7300-37A Figure 1-5. Sector Format
1-4