Advanced I/O Controller with Motherboard GLUE Logic
Datasheet
6.14 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
6.15 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.
6.16 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, the TC cycle 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 6.22 and Table 6.23 for information
concerning the values of MT and EC versus SC and EOT value.
Definitions:
# 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”.
Revision 1.8 SMSC/Non-SMSC Register Sets (02-24-05)
68
SMSC LPC47M182
DATASHEET
SMSC [ SMSC CORPORATION ]
