Read after write enhancement for bit patterned media

• US 20090002868A1
• Filed: 06/29/2007
• Published: 01/01/2009
• Est. Priority Date: 06/29/2007
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Mallary, Michael L., He, Ching, Vanlaanen, John W.
• Granted Patent: US 8,035,910 B2
• Time in Patent Office: Days
• US Class Current: 360/55
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G11B 20/10398 jitter, timing deviations or phase and frequency errors
• CPC Class Codes: G11B 20/10509 iterative methods, e.g. trial-and-error, interval search, gradient descent or feedback loops G11B20/10518 takes precedence
• CPC Class Codes: G11B 20/1879 Direct read-after-write methods
• CPC Class Codes: G11B 2220/252 Patterned or quantised magnetic media, i.e. bits are stored in predefined single domain elements
• CPC Class Codes: G11B 5/012 Recording on, or reproducing or erasing from, magnetic disks G11B17/00, G11B19/00 take precedence
• CPC Class Codes: G11B 5/02 Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
• CPC Class Codes: G11B 5/3948 the sensitive elements being active read-out elements
• CPC Class Codes: G11B 5/59616 Synchronisation; Clocking G11B5/59622 takes precedence
• CPC Class Codes: G11B 5/59638 Servo formatting apparatuses, e.g. servo-writers
• CPC Class Codes: G11B 5/746 Bit Patterned record carriers, wherein each magnetic isolated data island corresponds to a bit
• CPC Class Codes: G11B 5/82 Disk carriers

Abstract

A read/write head for use with bit-patterned media detects write synchronization errors between a write clock and the bit-patterned media. In particular, the read/write head writes data to the bit-patterned media using a write clock. The data is then read from the bit-patterned media and used to detect write synchronization errors between the write clock and the location of bit-islands on the bit-patterned media. Based on detected write synchronization errors, the phase associated with the write clock is modified to align the write clock with the location of bit-islands on the bit-patterned media.

Claims

1. A method for detecting write synchronization errors in bit-patterned media, the method comprising:

writing data to a bit-patterned media with a write clock;

reading data written to the bit-patterned media to detect write synchronization errors associated with the write clock being out of phase with the location of bit-islands on the bit-patterned media; and

modifying the phase of the write clock based on detected write synchronization errors.

2. The method of claim 1, wherein reading data written to the bit-patterned media includes:

employing a read/write head having a first reader positioned behind the writer such that the first reader provides read after write (RAW) verification of the data written by the writer.

3. The method of claim 2, wherein a distance separating the writer from the first reader is minimized to reduce effects of skew between the writer and the first reader such that the first reader is positioned as close as possible to a track written by the writer.

4. The method of claim 2, wherein reading data written to the bit-patterned media includes:

subtracting noise associated with the data currently being written by the writer to reduce cross-talk between the first reader and the writer.

5. The method of claim 2, wherein reading data written to the bit-patterned media includes:

reading only that data written to the bit-patterned media that passes under the first reader following the writer ceasing to write data to the bit-patterned media.

6. The method of claim 1, wherein reading data written to the bit-patterned media includes:

employing a read/write head having a first reader positioned behind the writer and a second reader positioned behind the writer and radially offset from the first reader such that the first reader and the second reader provide read after write (RAW) verification of the data written by the writer.

7. The method of claim 6, further including:

generating error positioning signal regarding the radial position of the read/write head based on a ratio of magnitudes of on-track signals measured by both the first reader and the second reader.

8. The method of claim 6, further including:

generating error positioning data regarding the radial position of the read/write head based on a magnitude of cross talk relative to an on-track signal as measured by both the first reader and the second reader.

9. The method of claim 1, wherein the bit-patterned media includes normally positioned bit-islands, early positioned bit-islands shifted in a first direction relative to the normally positioned bit-islands, and late positioned bit-islands shifted in a second direction relative to the normally positioned bit-islands.

10. The method of claim 9, wherein reading data written to the bit-patterned media to detect write synchronization errors associated with the write clock being out of phase with the location of bit-islands on the bit-patterned media includes:

reading the data written to the early positioned bit-islands and the data written to the late positioned bit-islands to detect write synchronization errors based on the success or failure to write bits to either the early positioned bit-islands or the late positioned bit-islands.

11. The method of claim 10, wherein modifying the phase of the write clock based on detected write synchronization errors includes:

modifying the phase of the write clock based on the success or failure to write bits to either the early positioned bit-islands or the late positioned bit-island such that the write clock is properly phased with the normally positioned bit-islands of the bit-patterned media.

12. The method of claim 1, wherein writing data to the bit-patterned media with a write clock includes:

modifying the phase of the write clock to include a normally phased write clock, an early phased write clock, and a late phased write clock.

13. The method of claim 12, wherein reading data written to the bit-patterned media to detect write synchronization errors includes:

reading the data written to the bit-patterned media with the early phased write clock and the data written to the bit-patterned media with the late phased write clock to detect write synchronization errors based on the success or failure to write bits with the early phased write clock or the late phased write clock.

14. The method of claim 13, wherein modifying the phase of the write clock based on detected write synchronization errors includes:

modifying the phase of the write clock based on the success or failure to write bits with the early phased write clock or the late phased write clock.

15. A read/write head for providing read after write functionality, the read/write head comprising:

a writer for writing data to a bit patterned media using a write clock; and

a first reader for reading data stored to the bit patterned media and positioned behind the writer such that the first reader can provide real-time verification of data written by the writer.

16. The read/write head of claim 15, wherein a distance separating the write from the first reader is minimized to reduce effects of skew between the writer and the first reader such that the first reader is positioned as close as possible to a track written by the writer.

17. The read/write head of claim 15, further including:

a synthetic anit-ferromagnet write shield located between the first reader and the writer; and

a synthetic anit-ferromagnet write bottom reader shield located between the write shield and the first reader.

18. The read/write head of claim 15, wherein the cross-talk between the writer and the first reader is reduced by subtracting noise associated with the data currently being written by the writer.

19. The read/write head of claim 15, wherein the first reader only reads data subsequent to the write head ceasing write operations, wherein the first reader verifies all remaining data that passes under the first reader.

20. The read/write head claim of 15, further including:

a second reader offset radially from the first reader, wherein the first reader and the second reader work in conjunction to read the data written by the writer in a ganged read after write configuration.

21. The read/write head of claim 20, wherein an error positioning signal regarding the radial position of the read/write head is determined based on a ratio of off-track signals measured by the first reader and the second reader.

22. The read/write head of claim 20, wherein error positioning data regarding the radial position of the read/write head is determined based on a ratio of on-track signals measured by the first reader and the second reader.