LPC47M182 datasheet(68/223 Pages) SMSC

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Advanced I/O Controller with Motherboard GLUE Logic

Datasheet

Revision 1.8 SMSC/Non-SMSC Register Sets (02-24-05)

SMSC LPC47M182

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”.

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