FDC37B77X View Datasheet(PDF) - SMSC -> Microchip
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Description
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FDC37B77X Datasheet PDF : 196 Pages
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then the head settling time may be saved
between subsequent reads.
If the FDC detects a pulse on the nINDEX pin
twice without finding the specified sector
(meaning that the diskette's index hole passes
through index detect logic in the drive twice), the
FDC sets the IC code in Status Register 0 to
"01" indicating abnormal termination, sets the
ND bit in Status Register 1 to "1" indicating a
sector not found, and terminates the Read Data
Command.
After reading the ID and Data Fields in each
sector, the FDC checks the CRC bytes. If a
CRC error occurs in the ID or data field, the
FDC sets the IC code in Status Register 0 to
"01" indicating abnormal termination, sets the
DE bit flag in Status Register 1 to "1", sets the
DD bit in Status Register 2 to "1" if CRC is
incorrect in the ID field, and terminates the Read
Data Command. Table 21 describes the effect
of the SK bit on the Read Data command
execution and results. Except where noted in
Table 21, the C or R value of the sector address
is automatically incremented (see Table 23).
Table 20 - Effects of MT and N Bits
MAXIMUM TRANSFER
MT N
CAPACITY
FINAL SECTOR READ
FROM DISK
0 1 256 x 26 = 6,656
1 1 256 x 52 = 13,312
0 2 512 x 15 = 7,680
26 at side 0 or 1
26 at side 1
15 at side 0 or 1
1 2 512 x 30 = 15,360
0 3 1024 x 8 = 8,192
1 3 1024 x 16 = 16,384
15 at side 1
8 at side 0 or 1
16 at side 1
SK BIT
VALUE
0
0
1
1
Table 21 - Skip Bit vs Read Data Command
DATA ADDRESS
MARK TYPE
RESULTS
ENCOUNTERED
SECTOR CM BIT OF DESCRIPTION
READ? ST2 SET? OF RESULTS
Normal Data
Deleted Data
Yes
No
Normal
termination.
Yes
Yes
Address not
incremented.
Normal Data
Deleted Data
Next sector not
searched for.
Yes
No
Normal
termination.
No
Yes
Normal
termination.
Sector not read
("skipped").
53
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