Read Deleted Data
Table 25 describes the effect of the SK bit on the Read
Deleted Data command execution and results.
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
26).
Table 23 - Skip Bit vs. Read Deleted Data Command
DATA ADDRESS
RESULTS
SK BIT
VALUE
MARK TYPE
ENCOUNTERED
SECTOR CM BIT OF DESCRIPTION OF
READ?
ST2 SET?
RESULTS
0
Normal Data
Yes
Yes
Address not
incremented. Next
sector not
searched for.
Normal
termination.
Normal
0
1
Deleted Data
Normal Data
Yes
No
No
Yes
termination. Sector
not read
("skipped").
Normal
1
Deleted Data
Yes
No
termination.
Read A Track
and sets the 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".
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
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.
58
SMSC [ SMSC CORPORATION ]
