Open write-head-cable test method and detector

A storage drive implements a method for operating the storage drive between a plurality of operational modes. For a test mode of the storage drive, a write current driver circuit and a test current sensor are electrically connected to the write head, wherein the test current sensor generates a sense signal indicative of a degree of a flow of a test current through the write head to thereby facilitate a detection of any presence of an open write condition of the storage drive (i.e., any impedance condition impeding a flow of a write current through the write head). For a write mode of the storage drive, the write current driver circuit is electrically connected to the write head and the test current sensor is electrically disconnected from the write head, wherein the write head records data on a magnetic media based on a flow of the write current through the write head.

FIELD OF THE INVENTION

The present invention generally relates to a series of self-testing by a storage drive (e.g., a disk drive or a tape drive) to determine an operational capacity of a write head of the storage drive to record data on a magnetic media (e.g., a magnetic disk or a magnetic tape). The present invention specifically relates to a self-testing by a storage drive for any presence of an open write condition of the storage drive (i.e., any impedance condition of the storage drive impeding a flow of a write current through a write head.)

BACKGROUND OF THE INVENTION

Magnetic tape provides a means for physically storing data. As an archival medium, tape often comprises the only copy of the data. The tape is typically made as thin as practically possible to maximize the length of a tape stored on a tape reel, and thereby maximize the amount of data that can be stored on the tape contained in a single cartridge. A tape drive is used to store and retrieve data with respect to the magnetic tape. An example of a tape drive is the IBM TotalStorage Enterprise Tape Drive 3592 manufactured by IBM Corporation. Tape drives are typically used in combination with an automated data storage library. For example, the IBM TotalStorage Enterprise Tape Library 3494 manufactured by IBM Corporation is an automated data storage library that may include one or more tape drives and data storage media for storing data with respect to the tape drives.

FIG. 1illustrates an exemplary configuration of a known write mechanism of a tape drive employing a write current driver (“WCD”) circuit50having four (4) write current drivers in the form of an H-configuration of electronic switches S1-S4, which are electrically disconnected from a write head30. Under normal write conditions, opened electronic switches S1and S4can be closed as shown inFIG. 2to electrically connect write current driver circuit50to Write head30via a drive card40and a pair of cables C1and C2whereby a write current IWflows from a power supply60through write head30to a power return61in a first direction as indicated by the arrows. Similarly, opened electronic switches S2and S3can be closed as shown inFIG. 3to electrically connect write current driver circuit50to write head30via drive card40and cables C1and C2whereby write current IWflows from power supply60through write head30to power return61in a second opposing direction as indicated by the arrows.

Under an open write condition, the write current IWwill not flow through write head30upon a closing of electronic switches S1and S4or a closing of electronic switches S2and S3. For example, as shown inFIG. 4, an open condition OC1of write head30, an open condition OC2of cable C1and/or an open condition OC3of drive card40will impede a flow of write current IWfrom power supply60through write head30to power return61. Consequently, the storage industry is constantly striving to improve upon techniques for detecting a presence of an open write condition of a storage drive.

SUMMARY OF THE INVENTION

Various embodiments of the present invention provide a new and unique technique for detecting any presence of an open write condition of a storage drive (i.e., any impedance condition of the storage drive impeding a flow of a write current through a write head.)

A first form of the present invention is a method for operating a storage drive (e.g., a disk drive or a tape drive) between a plurality of operational modes. For a test mode of the storage drive, a write current driver circuit and a test current sensor are electrically connected to a write head, wherein the test current sensor generates a sense signal indicative of a degree of a flow of a test current through the write head. For a write mode of the storage drive, the write current driver circuit is electrically connected to the write head and the test current sensor is electrically disconnected from the write bead, wherein the write head records data on a magnetic media (e.g., a magnetic disk or a magnetic tape) based on a flow of a write current through the write head.

A second form of the present invention is a storage drive (e.g., a disk drive or a tape drive) having a plurality of operational modes. The storage drive comprises a write head, a write current driver circuit and a test current sensor. For a test mode of the storage drive, a write current driver circuit and a test current sensor are electrically connected to a write head, wherein the test current sensor generates a sense signal indicative of a degree of a flow of a test current through the write head. For a write mode of the storage drive, the write current driver circuit is electrically connected to the write head and the test current sensor is electrically disconnected from the write head, wherein the write head records data on a magnetic media (e.g., a magnetic disk or a magnetic tape) based on a flow of a write current through the write head.

A third form of the present invention is a storage system (e.g., a disk system or a tape system) having a plurality of operational modes. The storage system comprises a write controller, a write head, a write current driver circuit and a test current sensor. For a test mode of the storage system, a write controller electrically connects the write current driver circuit and the test current sensor to the write head, wherein the test current sensor generates a sense signal indicative of a degree of a flow of a test current through the write head. For a write mode of the storage system, the write controller electrically connects the write current driver circuit to the write head and electrically disconnects the test current sensor from the write head, wherein the write head records data on a magnetic media (e.g., a magnetic disk or a magnetic tape) based on a flow of a write current through the write head.

The aforementioned forms and additional forms as well as objects and advantages of the present invention will become further apparent from the following detailed description of the various embodiments of the present invention read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the present invention rather than limiting, the scope of the present invention being defined by the appended claims and equivalents thereof.

DETAILED DESCRIPTION

FIG. 5illustrates an integration of an open write condition detector70into the storage drive ofFIG. 1. Detector70employs a test current driver in the form of an electronic switch S5and a test current sensor71to detect a presence of any open write condition of the storage drive. With this integration, the storage drive operates between an idle mode, a test mode and a write mode.

Specifically, referring to an operational mode table80shown inFIG. 6, the idle mode of the storage drive encompasses electronic switches S1-S5being in an open state whereby write current driver circuit50and test current sensor70are electrically disconnected from write head30as shown inFIG. 5. The test mode of the storage drive encompasses electronic switches S1and S5being in a closed state and electronic switches S2-S4being in an open state whereby write current driver circuit50and test current sensor70are electrically connected to write head30as shown inFIGS. 8 and 9. The write mode of the storage drive includes electronic switch S5being in an open state with electronic switches S1and S4being in a closed state and electronic switches S2and S3being in an open state as shown inFIG. 10, or with electronic switches S1and S4being in an open state and electronic switches S2and S3being in a closed state as shown inFIG. 11.

For the test mode, a flowchart90shown inFIG. 7is representative of an open write condition detection method of the present invention. Specifically, a stage S92of flowchart90encompasses a controller (not shown) providing control signals (e.g., logic signals) to electronic switches S1-S5to close switches S1and S5and maintain switches S2-S4in an open state as shown inFIGS. 8 and 9. During a stage S94of flowchart90, test current sensor71generates a sensing signal SS indicative of a degree of flow of a test current ITthrough write head30, and compares sensing signal SS to a reference signal RS representative of a flow of write current IWthrough write head30under normal write conditions. If the comparison of sensing signal SS and reference signal RS indicates the flow of test current ITthrough write head30is equivalent to the flow of write current IWthrough write head30under a normal write condition (i.e., test current IT≈write current IW), then test current sensor71generates a test current pass indicator TCP as shown inFIG. 8that is communicated to the controller for purposes of informing the controller of the normal write condition of the storage drive. As a result, the controller understands that it can operate the storage drive in the write mode as shown inFIGS. 10 and 11.

Conversely, if the comparison of sensing signal SS and reference signal RS indicates the flow of test current ITthrough write head30is unequivalent to the flow of write current IWthrough write head30under a normal write condition (i.e., test current IT=0 or is significantly less than write current IW), then test current sensor71generates a test current failure indicator TCF as shown inFIG. 9that is communicated to the controller for purposes of informing the controller of the open write condition of the storage drive. As a result, the controller understands that it can not operate the storage drive in the write mode as shown inFIGS. 10 and 11.

In practice, there are no limitations or restrictions to the structural configurations of a write current driver circuit50and an open write condition detector70as shown in FIGS.5and8-11in implementing the open write condition detection method shown inFIG. 7. To further illustrate an understanding of the open write condition detection method,FIG. 12illustrates an exemplary structural configuration of write current driver circuit50as a known voltage mode current driving device having a H configuration of a pair of NFETs M1and M2and a pair of PFETs M3and M4for selectively applying a voltage source VSto a DC series resistance/inductance load R6/LI of write head30via driver card40represented by resistors R3-R5and via cables C1and C2.

Also shown inFIG. 12is an exemplary structural configuration of open write condition detector70employing a pair of test current drivers in the form of a NFET M5and a PFET M6, a voltage generator having a pair of resistors R1and R2and a voltage comparator U1. FETs M5and M6are electrically connected in parallel and are electrically connected in series with a parallel electrical connection of resistors R1and R2that generate a test voltage VTat an inverting input (−) of voltage comparator U1. A programmable reference voltage VRrepresentative of a flow of write current IWthrough write head30is applied to a non-inverting input (+) of voltage comparator U1whereby voltage comparator U1generates a test current indicator TCI based on a comparison of test voltage VTto a reference voltage VR.

With this integration, the storage drive operates between an idle mode, a test mode and a write mode in accordance with an operational mode table100shown inFIG. 13. Specifically, the idle mode of the storage drive encompasses FETs M1-M6being in non-conductive state (“NONC ST”) whereby write current driver circuit50and test current sensor70are electrically disconnected from write head30as shown inFIG. 15. This is accomplished by an application of a disable logic level of gate signals PN, MN, PP, MP, POT and MOT to the respective gates of FETs M1-M6.

The test mode of the storage drive encompasses FETs M3, M5and M6being in a conductive state (“COND ST”) and FETs M1, M2and M4being in a non-conductive state whereby write current driver circuit50and test current sensor70are electrically connected to write head30as shown inFIGS. 16 and 17. This is accomplished by an application of an enable logic level of gate signals PP, POT and MOT to the respective gates of FETs M3, M5and M6, and by an application of a disable logic level of gate signals PN, MN and MP to the respective gates of FETs M1, M2and M4.

The write mode of the storage drive includes FETs M5and M6being in a non-conductive state with FETs M1and M4being in a non-conductive state and FETs M2and M3being in a conductive state as shown inFIG. 18, or with FETs M1and M4being in a conductive state and FETs M2and M3being in a non-conductive state as shown inFIG. 19. This is accomplished by an application of a disable logic level of gate signals POT and MOT to the respective gates of FETs M5and M6with either an application of a disable logic level of gate signals PN and MP to the respective gates of FETs M1and M4and an application of enable logic level of gate signals PP and MN to the respective gates of FETs M2and M4, or with an application of an enable logic level of gate signals PN and MP to the respective gates of FETs M1and M4and an application of a disable logic level of gate signals PP and MN to the respective gates of FETs M2and M3.

For the test mode, a flowchart110shown inFIG. 14is representative of an open write condition detection method of the present invention. Specifically, a stage S112of flowchart110encompasses a controller (not shown) providing the gate signals to FETs M1-M6to transition FETs M3, M5and M6to a conductive state and to maintain FETs M1, M2and M4in a non-conductive state as shown inFIGS. 16 and 17. During a stage S114of flowchart110, test voltage VTis indicative of a degree of flow of a test current ITthrough write head30, and compares test voltage VTto a reference voltage VR, which is representative of a flow of write current IWthrough write head30under normal write conditions. If the comparison of test voltage VTand reference voltage VRindicates the flow of test current ITthrough write head30is equivalent to the flow of write current IWthrough write head30under a normal write condition (i.e., test current IT≈write current IW), then voltage comparator U1generates test current indicator TCI as a test current pass indicator of a logic low level (“0”) as shown inFIG. 16that is communicated to the controller for purposes of informing the controller of the normal write condition of the storage drive. As a result, the controller understands that it can operate the storage drive in the write mode as shown inFIGS. 18 and 19.

Conversely, if the comparison of test voltage VTand reference voltage VRindicates the flow of test current ITthrough write bead30is unequivalent to the flow of write current IWthrough write head30under a normal write condition (i.e., test current IT=0 or is significantly less than write current IW), then voltage comparator U1generates test current indicator TCI as a test current failure indicator of a logic low level (“1”) as shown inFIG. 17that is communicated to the controller for purposes of informing the controller of the open write condition of the storage drive. As a result, the controller understands that it can not operate the storage drive in the write mode as shown inFIGS. 18 and 19.

Referring to FIGS.12and15-19, resistors R1-R6and inductor L1may be chosen to optimize the circuit depending on the desired write current and write frequency of the application. Typical values for the embodiment herein described are as follows. The write clock cycle frequency is in the range of 120-350 MHz. Voltage source VSis programmable in the range of 3-6 volts in order to change the magnitude of write current IWand test current ITby as much as 40-50%. Resistors R1and R2have a resistance of 200Ω, resistors R3and R5have a resistance of 100Ω, resistor R4has a resistance of 255Ω, resistor R6has a resistance of 25Ω, and inductor L1has an inductance of 150 nanohenries. As such, reference voltage VRis in the range of 0.4 to 0.8 volts, preferably 0.6 volts.

FIG. 20illustrates a current mode H configuration write current driver circuit that is similar to the voltage mode H configuration write current driver circuit shown inFIG. 12with the exceptions of (1) an elimination of resistors R3and R5, and (2) source electrodes of NFETs M1and M2being connected to a current source ISinstead of ground. Current source ISmay be programmable in a typical range of 10 to 50 milliamps in order to change the magnitude of write current IW.

FIG. 21illustrates an embodiment of a magnetic tape recorder or tape drive system120incorporating an open write condition detector (“OWCD”)200of the present invention. A tape drive controller122provides a motor control signal to rotate tape reels124and move magnetic tape123across the read/write transducer head121. Read/write channel125transmits read/write signals between the read/write transducer121and the controller122. The data is communicated through I/O channel129with host131. Lateral positioning of the transducer121with respect to the tape123is accomplished by positioning actuator127. The lateral repositioning is required to access the various tracks of the tape123with the transducer121. A servo system may be employed for accurate lateral repositioning of the transducer121. An exemplary servo system includes a servo detector126to detect both the track that the head is currently on and whether the head is off center. Controller122indicates the track address of a desired new track to position error detection controller128for repositioning the head. Servo detector126indicates the current track to position error detection controller128, and the controller provides a servo position error signal to positioning actuator127which repositions the transducer121to the new track. The servo system also provides track following signals to positioning actuator127so that the tracks on tape123may be closely spaced. Controller122uses logic control signals at Power on Reset to activate detector200whereby, upon a detection of an open write condition, controller122will report a RAS error to thereby flag a need for drive200to be serviced or replaced.

Referring toFIGS. 5-20, those having ordinary skill in the art will appreciate numerous benefits and advantages of the illustrated embodiments of the present invention including, but not limited to, an efficient and effective technique for detecting an open write condition of a storage drive. Those having ordinary skill in the art will further appreciate how to implement the inventive principles of the present invention to driver circuits more or less complex than the driver circuits illustrated throughoutFIGS. 5-20.

Those having ordinary skill in the art may develop other embodiments of the present invention in view of the inventive principles of the present invention described herein. The terms and expression which have been employed in the foregoing specification are used herein as terms of description and not of limitations, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or segments thereof; it being recognized that the scope of the invention is defined and limited only by the claims which follow.