Write Data
•
Definition of DTL when N = 0 and when N
does not = 0
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.
Write Deleted Data
This command is almost the same as the Write
Data command except that a Deleted Data
Address Mark is written at the beginning of the
Data Field instead of the normal Data Address
Mark. This command is typically used to mark a
bad sector containing an error on the floppy disk.
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
Verify
The Verify command is used to verify the data
stored on a disk. This command acts exactly like
a Read Data command except that no data is
transferred to the host. Data is read from the disk
and CRC is computed and checked against the
previously-stored value.
Because data is not transferred to the host, TC
(pin
89) cannot be used to terminate this
command. By setting the EC bit to "1", an implicit
TC will be issued to the FDC. This implicit TC
will occur when the SC value has decremented
to 0 (an SC value of 0 will verify 256 sectors). This
command can also be terminated by setting the
EC bit to "0" and the EOT value equal to the final
sector to be checked. If EC is set to "0", DTL/SC
should be programmed to 0FFH. Refer to Table
23 and Table 24 for information concerning the
values of MT and EC versus SC and EOT value.
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:
Definitions:
•
•
•
•
•
Transfer Capacity
EN (End of Cylinder) bit
ND (No Data) bit
Head Load, Unload Time Interval
ID information when the host terminates the
command
# Sectors Per Side = Number of formatted sectors
per each side of the disk.
# Sectors Remaining = Number of formatted
sectors left which can be read, including side 1 of
the disk if MT is set to "1".
58
SMSC [ SMSC CORPORATION ]
