
Advanced Notebook I/O for ISA or LPC Designs
Datasheet
Rev. 0.5 (03-24-05)
Page 80
SMSC SIO10N268
DATASHEET
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 8.25 describes the effect
of the SK bit on the Read Data command execution and results. Except where noted in Table 8.25, the C
or R value of the sector address is automatically incremented (see Table 8.27).
Table 8.24 - Effects of MT and N Bits
MT
N
MAXIMUM TRANSFER
CAPACITY
FINAL SECTOR READ
FROM DISK
0
1
0
1
0
1
2
3
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
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
Table 8.25 - Skip Bit vs Read Data command
SK BIT
VALUE
DATA ADDRESS
MARK TYPE
ENCOUNTERED
RESULTS
SECTOR
READ?
CM BIT OF
ST2 SET?
DESCRIPTION OF
RESULTS
0
Normal Data
Yes
No
Normal
termination.
0
Deleted Data
Yes
Address not
incremented. Next
sector not
searched for.
1
Normal Data
Yes
No
Normal
termination.
1
Deleted Data
No
Yes
Normal
termination. Sector
not read
("skipped").
8.7.7.2
Read Deleted Data
This command is the same as the Read Data command, only it operates on sectors that contain a Deleted
Data Address Mark at the beginning of a Data Field.
Table 8.26 describes the effect of the SK bit on the Read Deleted Data command execution and results.
Except where noted in Table 8.26, the C or R value of the sector address is automatically incremented
(see Table 8.27).