HP 7936 Support Manual page 40

Functional Description
7936 and 7937
PLL SYNC
SYNC FIELD WORD
BYTES: 13
[!]
SYNC FIELD
DATA
TYPICAL SECTOR
(1 OF 124)
POST AMBLE
I I
CRC ECC DATA SERVO SERVO
GAP SYNC CODE
2 12
SPARE HEAD SECTOR STATUS CYL CYL
SECTOR (MSB) (LSB)
FOR SYNCHRONIZATION OF READ CIRCUIT
PHASE-LOCKED LOOP (~LL).
• PPL SYNC FIELD TO ACHIEVE PHASE LOCK.
rn
rn
0
@]
[§]
0
S7tJ7A13
[§]
5-6
• SYNC WORD SIGNALS START OF DATA FIELD.
HEADER
• SPARE SECTOR
• HEAD
• SECTOR
• STATUS
• CYL (MSB)
• CYL (LSB)
DATA
CRC
ECC
DATA GAP
SERVO SYNC
SERVO CODE
STATUS AND ADDRESS INFORMATION.
PHYSICAL ADDRESS OF SPARED SECTOR ON TRACK.
(WILL BE 123 IF NO SECTOR SPARING DONE.)
LOGICAL HEAD ADDRESS.
PHYSICAL SECTOR ADDRESS.
TRACK STATUS.
BIT 7: 1-PRIMARY TRACK SPARE· O-SECONDARY TRACK SPARE.
BIT 6: 1-PRIMARY SECTOR
SPAR~;
O-SECONDARY SECTOR SPARE.
LOGICAL CYLINDER ADDRESS (MSB).
LOGICAL CYLINDER ADDRESS (LSB).
READ/WRITE DATA.
CYCLIC REDUNDANCY CHECK. ERROR CHECKING INFORMATION.
ERROR CORRECTION CODE. ERROR CHECKING AND CORRECTIONS.
ECC WILL CORRECT UP TO SIX DATA BYTES PER SECTOR.
THE ByTES NEED NOT BE CONTIGUOUS.
ALLOWS TIME TO SWITCH FROM WRITE MODE (DURING A
WRITE) TO READ MODE WHILE SEPARATING DATA FROM
SERVO INFORMATION.
CONTAINS A QUALIFICATION PULSE AND A SYNC PULSE TO
TRIGGER THE START OF SAMPLED SERVO READING.
SAMPLED SERVO CODE.
FIgure
5- .
Sector Format