JPH0142072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention provides an offset seek function (that is, a head that is accessing a target track is slightly shifted in position to read data recorded off-center from the center of the track). The present invention relates to a magnetic disk device having an offset seek function, and more particularly to a magnetic disk device that performs an offset seek operation to provide compatibility with magnetic disk devices that do not have an offset seek function.

(b) Prior Art and Problems Large-capacity magnetic disk drives generally have a servo zone for positioning the head, separate from the data zone for writing and reading data. The head is positioned to each track to which it belongs.

FIG. 1 is a schematic diagram of a magnetic disk device having a servo zone. 1 is a voice coil motor and 2
and positioning of each magnetic head shown in 3.
2 is a head for writing/reading data, and 3 is a servo head. 4 indicates a data zone of the magnetic disk, and 5 indicates a servo zone. The servo signal in the servo zone 5 is read out by the servo head 3, and the head 2 accesses the track on the same cylinder. However, due to various mechanical factors, the position of a track in a data zone on a magnetic disk disk may deviate from the position of the corresponding servo zone, and previously written data may be displaced from the track positioned by the servo zone. A phenomenon may occur in which the center of the image is not recorded.
In such a case, the data can be read by slightly shifting the position of the head 2 accessing the track. The function of shifting the position of the head 2 from the position determined by the servo zone in this manner is called offset seek. Generally, as the track density increases, the width of each track becomes narrower, making it easier for relative positional deviations to occur. By the way, in order to increase the storage capacity while maintaining control compatibility with the conventional model, having the same magnetic disk disk diameter, and the same transfer speed, the only way to increase the storage capacity is to increase the track density. However, since a magnetic disk device with increased track density as described above requires an offset seek function, it has the disadvantage that it is not compatible with conventional magnetic disk devices that do not have an offset seek function.

(c) Purpose of the Invention The purpose of the present invention is to eliminate the above-mentioned drawbacks by enabling offset seek control on the magnetic disk device side, thereby controlling a conventional magnetic disk device that does not have an offset seek function. It is an object of the present invention to provide a magnetic disk device having an offset seek function that can be connected to a magnetic disk control device without changing the control microprogram.

(d) Structure of the invention It has a servo signal separate from the data signal, has a closed loop servo mechanism using a voice coil motor as an actuator for positioning the data head on a specific track, and has a biased position signal generated from the servo signal. A magnetic disk drive having an offset seek function for displacing the position of the data head in the radial direction of the disk by adding means and
means for determining, based on the determination by the determining means, that a record cue command from the magnetic disk controller is an instruction to retry data reading; and a data read operation to be retried based on the determination by the determining means. means for counting the number of times, and means for activating the offset seek function by changing the direction and amount of displacement of the data head according to the number of times counted by the counting means during the record cueing operation,
The magnetic disk device is configured to perform an offset seek operation.

(e) Embodiments of the Invention The present invention detects a state in which an offset seek is required on the magnetic disk device side, and issues an offset seek command. Then, the read operation following the command is monitored, and if necessary, the offset seek direction or offset amount is changed and the offset seek command is issued again. Or, in some cases, the offset state is canceled and the head is returned to the center of the track.

The conditions for starting the offset seek function in this embodiment are as follows.

A data check occurred while reading data with the magnetic disk device, and although the ECC (error correction code) was analyzed, correct data could not be obtained.
When a set target command is issued from the magnetic disk controller to search for a target record for retry, the sequencer provided in the magnetic disk device or adapter starts operating.

Further, the conditions for terminating the offset seek operation in this method are as follows.

Retries reached the specified number of times and the game was retryed out.

The head of the magnetic disk device has been switched.

The magnetic disk device performed a seek (positioning operation of the head) or a rezero (operation of returning the REZERO head to cylinder O).

The magnetic disk device has been deselected (deselected).

The retry was successful and the next read/write command was issued.

If any of the above five conditions apply, the sequencer ends its operation.

FIG. 2 is a block diagram of a circuit showing one embodiment of the present invention. When a read command is input to terminal R from the magnetic disk controller, flip-flop 7 is set. When this read command is normally completed, a normal end is issued from the adapter to the magnetic disk controller, which enters the terminal NE and resets the flip-flop 7 via the OR circuit 6, and also resets the flip-flop 22 via the OR circuit 23. However, the read command did not complete normally and a data check, no address mark found (address mark could not be detected), or no synchro byte found (synchro byte could not be detected) occurred. When this occurs and the data read command ends abnormally, a data check is sent to the terminal DC, a no address mark found is sent to the terminal NAMF, and a no address mark is sent to the terminal NSBF.
The synchro byte found is input, passes through the OR circuit 8, and is output from the flip-flop 11 by setting the AND9 to "1" along with the output of the terminal Q of the flip-flop 7.
Set. When flip-flop 11 is set, flip-flop 7 is reset via OR circuit 6. When a read command ends abnormally due to a data check, the magnetic disk controller causes the ECC to be analyzed, but when the command enters the terminal ECC,
Set the flip-flop 22. If the data error can be corrected by ECC analysis, an index alert signal is input from the magnetic disk controller to terminal IA, and the AND circuit 21 is set to "1".
The flip-flop 11 is reset via the OR circuit 10. By resetting the flip-flop 11, the terminal becomes "1" and goes through the OR circuit 23 to reset the flip-flop 22. If the data error cannot be corrected by ECC analysis, a normal end is issued as described above, and the OR
Flip-flops 7 and 22 are reset via circuits 6 and 23, respectively. In the case of no address, mark, found, no synchronization, byte, found, and data errors cannot be corrected by ECC analysis, the magnetic disk control device reads the beginning of the record that records the target data in order to perform a reread operation. A set target command is issued to cause the magnetic disk device to search for the target. terminal
The set target command entered in ST causes the AND circuit 12 to become "1" and the flip-flop 14 to be set. The sequencer 16 is activated by setting the flip-flop 14, and at the same time, the flip-flop 11 is reset via the OR circuit 10. The activated sequencer 16 sets the flip-flop 17 and resets the flip-flop 14 via the OR circuit 13. If the flip-flop 14 is set again while the flip-flop 17 is set, this indicates that the re-read operation is the second or subsequent time.

The sequencer 16 increments the counter 15 to count the number of retries. Also, based on the number of times, the direction and amount of offset seek are determined and a command is issued, and the flip-flop 18 is reset via the OR circuit 20. When the head again reaches the beginning of the record, the magnetic disk device generates an interrupt to the magnetic disk controller, which issues a command to perform the read operation again, and sets the flip-flop 18 via the terminal RG. do. Sequencer 16 is flip-flop 1
When 8 is set, flip-flop 18 is reset through OR circuit 20, and flip-flop 1 is reset.
Watch for 4 to be set again. If the rereading operation is completed normally, the flip-flop 14 is not set, and after the rereading operation is completed, the flip-flop 14 is not set.
The flip-flop 18 is set again to process the next record, or a head switching command is issued to process the next track.
SHA or seek start command to terminal SS,
Alternatively, either a rezero start command is applied to the terminal RS, or a deselect command is applied to the terminal SH to complete the processing of the magnetic disk device. If flip-flop 14 is not set and flip-flop 18 is set again, sequencer 16 resets flip-flops 18 and 17 via OR circuits 20 and 19. Also terminal
If any of SHA, SS, RS, and SH becomes “1”
Flip-flop 1 via OR circuits 10 and 19
1 and 17 are reset.

If the reread operation fails, the flip-flop 14 is set again, the sequencer 16 enters the offset seek sequence again, and repeats the above operation. If the count value of the counter 15 reaches a predetermined number of retryouts, the sequencer 16 resets the flip-flops 14, 17, and 18, and after resetting the counter 15, returns to the non-operating state. When the power is turned on, a reset signal is input to terminal POR as an initial reset signal, passes through OR circuits 6, 10, 13, 19, 20, and 23, and then goes to flip-flops 7, 11, 14, 17, 18, and 2, respectively.
1 is reset.

(f) Effects of the Invention As explained above, the present invention provides an offset seek function to a magnetic disk control device that controls a magnetic disk device that does not have an offset seek function without changing the control microprogram. Since it is possible to connect and use magnetic disk devices with increased storage capacity,
The effect is great.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a magnetic disk device having a servo zone, and FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention. 1 is a voice coil motor, 2 is a write/read head, 3 is a servo head, 4 is a data zone,
5 is servo zone, 7, 11, 14, 17, 1
8 and 22 are flip-flops, 15 is a counter,
16 is a sequencer.

Claims (1)

[Claims] 1 It has a servo signal separate from the data signal, has a closed loop servo mechanism using a voice coil motor as an actuator that positions the data head on a specific track, and by adding a bias to the position signal generated from the servo signal, A magnetic disk device having an offset seek mechanism for displacing the position of a data head in the radial direction of the disk, comprising means for detecting a data read error, and means for determining whether the error is correctable or not.
means for determining, based on the determination by the determining means, that a record cue command from the magnetic disk controller is an instruction to retry data reading; and a data read operation to be retried based on the determination by the determining means. means for counting the number of times, and means for activating the offset seek function by changing the direction and amount of displacement of the data head according to the number of times counted by the counting means during the record cueing operation,
A magnetic disk device characterized in that the magnetic disk device performs an offset seek operation.