Data storage device demodulating digital data based on number of servo stripes in servo frame

1. A data storage device configured to access a magnetic tape comprising a plurality of servo frames each comprising a plurality of servo stripes, the data storage device comprising:

at least one head configured to access the magnetic tape; and

control circuitry configured to:

read the servo stripes using the head to generate a read signal;

process the read signal to generate a position error signal (PES);

control a position of the head relative to the magnetic tape based on the PES; and

demodulate the read signal into digital data based on a number of servo stripes detected in each servo frame.

2. The data storage device as recited in claim 1 , wherein the data storage device comprises the magnetic tape.

3. The data storage device as recited in claim 1 , wherein:

the magnetic tape is housed in a cartridge assembly; and

the data storage device comprises a tape drive assembly configured to receive the cartridge assembly.

4. The data storage device as recited in claim 1 , wherein each servo frame comprises:

a first subframe consisting of N servo stripes; and

a second subframe consisting of N−1 servo stripes when representing a first digital value or N−2 servo stripes when representing a second digital value.

5. The data storage device as recited in claim 4 , wherein:

N equals five;

the first digital value consists of a single bit; and

the second digital value consists of a single bit.

6. The data storage device as recited in claim 4 , wherein:

N equals seven;

the first digital value consists of two bits; and

the second digital value consists of two bits.

7. The data storage device as recited in claim 4 , wherein:

N equals nine;

the first digital value consists of four bits; and

the second digital value consists of four bits.

8. The data storage device as recited in claim 4 , wherein a width of the first subframe equals a width of the second subframe.

9. The data storage device as recited in claim 8 , wherein:

a format of the servo stripes in the first subframe matches a format of the servo stripes in the second subframe except for a single missing servo stripe when the number of servo stripes in the second subframe consists of N−1; and

a format of the servo stripes in the first subframe matches a format of the servo stripes in the second subframe except for two missing servo stripes when the number of servo stripes in the second subframe consists of N−2.

10. A magnetic tape comprising a plurality of servo frames for positioning at least one head over the magnetic tape, wherein each servo frame comprises:

a first subframe consisting of N servo stripes; and

a second subframe consisting of N−2 servo stripes when representing a digital value, wherein a spacing of the servo stripes of the first subframe and the servo stripes in the second subframe is constant.

11. The magnetic tape as recited in claim 10 , wherein:

N equals five; and

the digital value consists of a single bit.

12. The magnetic tape as recited in claim 10 , wherein:

N equals seven; and

the digital value consists of two bits.

13. The magnetic tape as recited in claim 10 , wherein:

N equals nine; and

the digital value consists of four bits.

14. The magnetic tape as recited in claim 10 , wherein a width of the first subframe equals a width of the second subframe.

15. The magnetic tape as recited in claim 14 , wherein:

a format of the servo stripes in the first subframe matches a format of the servo stripes in the second subframe except for a single missing servo stripe when the servo stripes in the second subframe consists of N−1 servo stripes; and

a format of the servo stripes in the first subframe matches a format of the servo stripes in the second subframe except for two missing servo stripes when the servo stripes in the second subframe consists of N−2 servo stripes.

16. A data storage device configured to access a magnetic tape comprising a plurality of servo frames each comprising a plurality of servo stripes, the data storage device comprising:

at least one head configured to access the magnetic tape; and

a means for demodulating digital data recorded in the servo frames.

17. The data storage device as recited in claim 16 , wherein the data storage device comprises the magnetic tape.

18. The data storage device as recited in claim 16 , wherein:

the magnetic tape is housed in a cartridge assembly; and

the data storage device comprises a tape drive assembly configured to receive the cartridge assembly.

19. The data storage device as recited in claim 16 , wherein each servo frame comprises:

a first subframe consisting of N servo stripes; and

a second subframe consisting of N−1 servo stripes when representing a first digital value or N−2 servo stripes when representing a second digital value.

20. The data storage device as recited in claim 19 , wherein:

N equals five;

the first digital value consists of a single bit; and

the second digital value consists of a single bit.

21. The data storage device as recited in claim 19 , wherein:

N equals seven;

the first digital value consists of two bits; and

the second digital value consists of two bits.

22. The data storage device as recited in claim 19 , wherein:

N equals nine;

the first digital value consists of four bits; and

the second digital value consists of four bits.

23. The data storage device as recited in claim 19 , wherein a width of the first subframe equals a width of the second subframe.

24. The data storage device as recited in claim 23 , wherein:

a format of the servo stripes in the first subframe matches a format of the servo stripes in the second subframe except for a single missing servo stripe when servo stripes in the second subframe consists of N−1 servo stripes; and

a format of the servo stripes in the first subframe matches a format of the servo stripes in the second subframe except for two missing servo stripes when the servo stripes in the second subframe consists of N−2 servo stripes.