FDC37B77X SMSC Corporation, FDC37B77X Datasheet - Page 53

• Manufacturer Part Number: FDC37B77X
• Description: ENHANCED SUPER I/O CONTROLLER WITH WAKE UP FEATURES
• Manufacturer: SMSC Corporation

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.
SK BIT
VALUE
0
0
1
1
MT
0
1
0
1
0
1
Normal Data
Deleted Data
Normal Data
Deleted Data
DATA ADDRESS
ENCOUNTERED
N
1
1
2
2
3
3
MARK TYPE
Table 21 - Skip Bit vs Read Data Command
256 x 26 = 6,656
256 x 52 = 13,312
512 x 15 = 7,680
512 x 30 = 15,360
1024 x 8 = 8,192
1024 x 16 = 16,384
MAXIMUM TRANSFER
Table 20 - Effects of MT and N Bits
CAPACITY
SECTOR
READ?
Yes
Yes
Yes
No
53
After reading the ID and Data Fields in each
sector, the FDC checks the CRC bytes.
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).
CM BIT OF
ST2 SET?
26 at side 0 or 1
26 at side 1
15 at side 0 or 1
15 at side 1
8 at side 0 or 1
16 at side 1
FINAL SECTOR READ
Yes
Yes
No
No
RESULTS
FROM DISK
Normal
termination.
Address not
incremented.
Next sector not
searched for.
Normal
termination.
Normal
termination.
Sector not read
("skipped").
DESCRIPTION
OF RESULTS
If a