TABLE 26 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 26, the C or R value
of the sector address is automatically incremented
(see Table 27).
TABLE 26 - 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
Address not
0
Normal Data
Yes
Yes
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.
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 ND flag of Status Register
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.
59
SMSC [ SMSC CORPORATION ]
