FDC37C78 datasheet(48/82 Pages) MICROCHIP

48 / 82 page

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.

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 25) 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

26 and Table 27 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".

Table 25 - Verify Command Result Phase Table

SC/EOT VALUE

TERMINATION RESULT

SC = DTL

EOT

≤ # Sectors Per Side

Success Termination

Result Phase Valid

SC = DTL

EOT > # Sectors Per Side

Unsuccessful Termination

Result Phase Invalid

≤ # Sectors Remaining AND

EOT

≤ # Sectors Per Side

Successful Termination

Result Phase Valid

SC > # Sectors Remaining OR

EOT > # Sectors Per Side

Unsuccessful Termination

Result Phase Invalid

SC = DTL

EOT

≤ # Sectors Per Side

Successful Termination

Result Phase Valid

SC = DTL

EOT > # Sectors Per Side

Unsuccessful Termination

Result Phase Invalid

≤ # Sectors Remaining AND

EOT

≤ # Sectors Per Side

Successful Termination

Result Phase Valid

SC > # Sectors Remaining OR

EOT > # Sectors Per Side

Unsuccessful Termination

Result Phase Invalid

NOTE: If MT is set to "1" and the SC value is greater than the number of remaining formatted sectors on

Side 0, verifying will continue on Side 1 of the disk.

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