FDC37C78 datasheet(46/82 Pages) MICROCHIP

46 / 82 page

Read Deleted Data

This command is the same as the Read Data

command, only it operates on sectors that contain

a Deleted Data Address Mark at the beginning of a

Data Field.

Table 2

3 describes the effect of the SK bit on the

Read Deleted Data command execution and

results.

Except where noted in Table 25, the C or R value

of the sector address is automatically incremented

(see Table 26).

Table 23 - Skip Bit vs. Read Deleted Data Command

DATA ADDRESS

RESULTS

SK BIT

VALUE

MARK TYPE

ENCOUNTERED

SECTOR

READ?

CM BIT OF

ST2 SET?

DESCRIPTION OF

RESULTS

Normal Data

Deleted Data

Normal Data

Deleted Data

Yes

Address not

incremented. Next

sector not

searched for.

Normal

termination.

Normal

termination. Sector

not read

("skipped").

Normal

termination.

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

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.

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