Table 25 describes the effect of the SK bit on
the Read Deleted Data command execution and
results.
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.
Except where noted in Table 25, the C or R
value of the sector address is automatically
incremented (see Table 25).
Table 25 - Skip Bit vs. Read Deleted Data Command
DATA ADDRESS
MARK TYPE
ENCOUNTERED
SK BIT
VALUE
RESULTS
SECTOR CM BIT OF
DESCRIPTION
OF RESULTS
READ?
ST2 SET?
0
Normal Data
Yes
Yes
Address not
incremented.
Next sector not
searched for.
Normal
0
1
Deleted Data
Normal Data
Yes
No
No
termination.
Normal
Yes
termination.
Sector not read
("skipped").
Normal
1
Deleted Data
Yes
No
termination.
ND flag of Status Register 1 to a "1" if there is
no comparison. Multi-track or skip operations
are not allowed with this command. The MT and
SK bits (bits D7 and D5 of the first command
byte respectively) should always be set to "0".
Read A Track
This command is similar to the Read Data
command except that the entire data field is
read continuously from each of the sectors of a
track. Immediately after encountering a pulse
on the nINDEX pin, the FDC starts to read all
data fields on the track as continuous blocks of
data without regard to logical sector numbers. If
the FDC finds an error in the ID or DATA CRC
check bytes, it continues to read data from the
track and sets the appropriate error bits at the
end of the command. The FDC compares the
ID information read from each sector with the
specified value in the command and sets the
This command terminates when the EOT
specified number of sectors has not been read.
If the FDC does not find an ID Address Mark on
the diskette after the second occurrence of a
pulse on the IDX pin, then it sets the IC code in
Status Register
0
to "01" (abnormal
termination), sets the MA bit in Status Register
1 to "1", and terminates the command.
57
SMSC [ SMSC CORPORATION ]
