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 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 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.
Table 41 - Result Phase Table
FINAL SECTOR
TRANSFERRED TO
MT
HEAD
HOST
ID INFORMATION AT RESULT PHASE
C
H
R
N
Less than EOT
NC
NC
R + 1
NC
0
0
Equal to EOT
C + 1
NC
NC
NC
01
NC
NC
Less than EOT
R + 1
1
0
1
Equal to EOT
C + 1
NC
NC
NC
01
NC
NC
Less than EOT
R + 1
1
Equal to EOT
NC
NC
LSB
NC
01
NC
NC
Less than EOT
R + 1
Equal to EOT
C + 1
LSB
01
NC
NC: No Change, the same value as the one at the beginning of command execution.
LSB: Least Significant Bit, the LSB of H is complemented.
Write Data
After the Write Data command has been issued, the FDC loads the head (if it is in the unloaded state), waits the
specified head load time if unloaded (defined in the Specify command), and begins reading ID fields. When the
sector address read from the diskette matches the sector address specified in the command, the FDC reads the data
from the host via the FIFO and writes it to the sector’s data field.
After writing data into the current sector, the FDC computes the CRC value and writes it into the CRC field at the end
of the sector transfer. The Sector Number stored in “R” is incremented by one, and the FDC continues writing to the
next data field. The FDC continues this “Multi-Sector Write Operation”. Upon receipt of a terminal count signal or if a
FIFO over/under run occurs while a data field is being written, then the remainder of the data field is filled with zeros.
The FDC reads the ID field of each sector and checks the CRC bytes. If it detects a CRC error in one of the ID fields,
it sets the IC code in Status Register 0 to “01” (abnormal termination), sets the DE bit of Status Register 1 to “1”, and
terminates the Write Data command.
The Write Data command operates in much the same manner as the Read Data command. The following items are
the same. Please refer to the Read Data Command for details:
Transfer Capacity
EN (End of Cylinder) bit
ND (No Data) bit
Head Load, Unload Time Interval
ID information when the host terminates the command
Definition of DTL when N = 0 and when N does not = 0
SMSC DS – FDC37N769
Page 48 of 137
Rev. 02-16-07
DATASHEET
SMSC [ SMSC CORPORATION ]
