Patterned media magnetic recording disk drive with write clock phase adjustment for data pattern circumferential misalignment
View Patent ↗A patterned-media magnetic recording disk drive compensates for circumferential misalignment of data island patterns among the data tracks as a result of errors in fabrication of the master template used to make the disks. Each data track on the disk has its pattern shifted from a generally radial or arcuate line by a certain amount of pattern circumferential misalignment (PCM). The disk drive includes a write clock where writing to the data islands is controlled by detection of synchronization marks by the read head, and circuitry to adjust the phase of the write clock to compensate for PCM. The phase difference between the data pattern of the selected data track where data is to be written and the data pattern of the track where the synchronization marks are being detected is the difference in their respective PCM values.
1. A magnetic recording disk drive comprising:
a rotatable magnetic recording disk having a plurality of generally circular data tracks and a plurality of angularly spaced synchronization marks extending generally radially across the data tracks, each data track patterned into discrete magnetizable data blocks, wherein the pattern of data blocks in a plurality of the data tracks is circumferentially misaligned;
a controller for selecting a data track where data is to be written;
a write head for writing data to a selected data track by generating write pulses to magnetize the data blocks in said selected data track;
a write clock coupled to the write head for controlling the write pulses to the data blocks;
a read head for sensing the synchronization marks;
synchronization mark detection circuitry coupled to the read head for controlling the write clock; and
phase adjustment circuitry responsive to the selected data track for adjusting the phase of the write clock to thereby correct for circumferential misalignment of the pattern of data blocks in said selected data track.
2. The disk drive of claim 1 wherein the value of data block pattern circumferential misalignment is a function of data track number and wherein the controller calculates the phase adjustment from the number of said selected data track.
3. The disk drive of claim 2 further comprising memory accessible by the controller, the memory containing a table of data track numbers and associated data block pattern circumferential misalignment values, and wherein the controller recalls from said table the data block pattern circumferential misalignment value associated with the data track number for said selected data track.
4. The disk drive of claim 1 wherein the read head is radially offset from the write head, each data track having an associated head radial offset value, and wherein the phase adjustment circuitry is responsive to the head radial offset value associated with said selected data track.
5. The disk drive of claim 4 wherein the value of data block pattern misalignment is a function of data track number and wherein the controller calculates the phase adjustment by calculating the difference in circumferential misalignment between the data block pattern of said selected data track and the data block pattern of the data track radially spaced from said selected data track by the value of the head radial offset associated with said selected data track.
6. The disk drive of claim 1 wherein the read head and write head are circumferentially offset from each other, each data track having an associated head circumferential offset value, and wherein the phase adjustment circuitry is responsive to the head circumferential offset associated with said selected data track.
7. The disk drive of claim 1 wherein the write clock has adjustable phases and the phase adjustment circuitry comprises a phase register, and wherein the phase of the write clock is adjusted by the value in said phase register.
8. The disk drive of claim 1 wherein the disk has generally equally angularly spaced servo sectors extending generally radially across the data tracks and containing positioning information for positioning the read head and write head on the data tracks, and wherein the synchronization marks are located within the servo sectors.
9. The disk drive of claim 1 wherein the data tracks are grouped into a plurality of radially spaced bands, and wherein the write clock frequency is unique for each of the bands.
10. A method for synchronizing the writing of data on discrete magnetizable data blocks of a patterned-media disk drive, the disk drive having (a) a rotatable magnetic recording disk having a plurality of generally circular data tracks and a plurality of angularly spaced synchronization marks extending generally radially across the data tracks, each data track patterned into discrete magnetizable data blocks wherein the pattern of data blocks in a plurality of the data tracks is circumferentially misaligned; (b) a write head for generating write pulses to magnetize the data blocks; (c) a write clock coupled to the write head for controlling the write pulses to the data blocks; (d) a read head for sensing the synchronization marks; (e) a processor for receiving synchronization mark signals from the read head and generating a phase adjustment signal to the write clock; and (f) memory coupled to the processor and containing a program of instructions readable by the processor; the processor-implemented method comprising:
identifying the selected data track on which data is to be written;
generating, from the selected data track, a write clock phase adjustment value representing the circumferential misalignment of the data block pattern in said selected track; and
transmitting to the write clock a phase adjustment signal representing said phase adjustment value.
11. The method of claim 10 wherein the memory contains a table of data track numbers and associated data block pattern circumferential misalignment values, and wherein generating a write clock phase adjustment value comprises recalling from said table the data block pattern circumferential misalignment value associated with the data track number for said selected data track.
12. The method of claim 10 wherein the read head is radially offset from the write head, each data track having an associated head radial offset value, and wherein generating said write clock phase adjustment value further comprises generating said write clock phase adjustment value from the head radial offset value associated with said selected data track.
13. The method of claim 12 wherein generating said write clock phase adjustment value comprises calculating the difference in circumferential misalignment between the data block pattern of the selected data track and the data block pattern of the data track radially spaced from said selected data track by the value of the head radial offset associated with said selected data track.
14. The method of claim 10 wherein the read head and write head are circumferentially offset from each other, each data track having an associated head circumferential offset value, and wherein the processor-implemented method further comprises generating, from the selected data track, a write clock phase adjustment value representing the head circumferential offset associated with said selected data track.
15. The method of claim 10 wherein the disk has generally equally angularly spaced servo sectors extending generally radially across the data tracks and containing positioning information for positioning the read head and write head on the data tracks, and wherein the synchronization marks are located within the servo sectors.
16. The method of claim 10 wherein the data tracks are grouped into a plurality of radially spaced bands, wherein the write clock frequency is unique for each of the bands, and wherein the method steps of identifying, generating and transmitting are performed in each of said bands.