Abstract:
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.

Description:
FIELD OF THE INVENTION 
       [0001]    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 
       [0002]    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. 
         [0003]      FIG. 1  illustrates an exemplary configuration of a known write mechanism of a tape drive employing a write current driver (“WCD”) circuit  50  having four (4) write current drivers in the form of an H-configuration of electronic switches S 1 -S 4 , which are electrically disconnected from a write head  30 . Under normal write conditions, opened electronic switches S 1  and S 4  can be closed as shown in  FIG. 2  to electrically connect write current driver circuit  50  to Write head  30  via a drive card  40  and a pair of cables C 1  and C 2  whereby a write current I W  flows from a power supply  60  through write head  30  to a power return  61  in a first direction as indicated by the arrows. Similarly, opened electronic switches S 2  and S 3  can be closed as shown in  FIG. 3  to electrically connect write current driver circuit  50  to write head  30  via drive card  40  and cables C 1  and C 2  whereby write current I W  flows from power supply  60  through write head  30  to power return  61  in a second opposing direction as indicated by the arrows. 
         [0004]    Under an open write condition, the write current I W  will not flow through write head  30  upon a closing of electronic switches S 1  and S 4  or a closing of electronic switches S 2  and S 3 . For example, as shown in  FIG. 4 , an open condition OC 1  of write head  30 , an open condition OC 2  of cable C 1  and/or an open condition OC 3  of drive card  40  will impede a flow of write current I W  from power supply  60  through write head  30  to power return  61 . 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 
       [0005]    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.) 
         [0006]    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. 
         [0007]    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. 
         [0008]    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. 
         [0009]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIGS. 1-4  illustrates a block diagram of a H configuration write current driver circuit as known in the art; 
           [0011]    FIGS.  5  and  8 - 11  illustrates a block diagram of one embodiment of a H configuration write current driver circuit having an integrated open write condition detector in accordance with the present invention; 
           [0012]      FIG. 6  illustrates a table listing various operating modes of the H configuration write current driver circuit having an integrated open write condition detector as illustrated in FIGS.  5  and  8 - 11 . 
           [0013]      FIG. 7  illustrates a flowchart representative of one embodiment of an open write condition detection method in accordance with the present invention; 
           [0014]    FIGS.  12  and  15 - 19  illustrates a schematic diagram of one embodiment of a H configuration voltage mode write current driver circuit having an integrated open write condition detector in accordance with the present invention; 
           [0015]      FIG. 13  illustrates a table listing various operating modes of the H configuration voltage mode write current driver circuit having an integrated open write condition detector as illustrated in FIGS.  12  and  15 - 19 ; 
           [0016]      FIG. 14  illustrates a flowchart representative of a second embodiment of an open write condition detection method in accordance with the present invention; 
           [0017]      FIG. 20  illustrates a schematic diagram of one embodiment of a H configuration current mode write current driver circuit having an integrated open write condition detector accordance with the present invention; and 
           [0018]      FIG. 21  illustrates a block diagram of one embodiment of a magnetic tape recorder system in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIG. 5  illustrates an integration of an open write condition detector  70  into the storage drive of  FIG. 1 . Detector  70  employs a test current driver in the form of an electronic switch S 5  and a test current sensor  71  to 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. 
         [0020]    Specifically, referring to an operational mode table  80  shown in  FIG. 6 , the idle mode of the storage drive encompasses electronic switches S 1 -S 5  being in an open state whereby write current driver circuit  50  and test current sensor  70  are electrically disconnected from write head  30  as shown in  FIG. 5 . The test mode of the storage drive encompasses electronic switches S 1  and S 5  being in a closed state and electronic switches S 2 -S 4  being in an open state whereby write current driver circuit  50  and test current sensor  70  are electrically connected to write head  30  as shown in  FIGS. 8 and 9 . The write mode of the storage drive includes electronic switch S 5  being in an open state with electronic switches S 1  and S 4  being in a closed state and electronic switches S 2  and S 3  being in an open state as shown in  FIG. 10 , or with electronic switches S 1  and S 4  being in an open state and electronic switches S 2  and S 3  being in a closed state as shown in  FIG. 11 . 
         [0021]    For the test mode, a flowchart  90  shown in  FIG. 7  is representative of an open write condition detection method of the present invention. Specifically, a stage S 92  of flowchart  90  encompasses a controller (not shown) providing control signals (e.g., logic signals) to electronic switches S 1 -S 5  to close switches S 1  and S 5  and maintain switches S 2 -S 4  in an open state as shown in  FIGS. 8 and 9 . During a stage S 94  of flowchart  90 , test current sensor  71  generates a sensing signal SS indicative of a degree of flow of a test current I T  through write head  30 , and compares sensing signal SS to a reference signal RS representative of a flow of write current I W  through write head  30  under normal write conditions. If the comparison of sensing signal SS and reference signal RS indicates the flow of test current I T  through write head  30  is equivalent to the flow of write current I W  through write head  30  under a normal write condition (i.e., test current I T ≈write current I W ), then test current sensor  71  generates a test current pass indicator TCP as shown in  FIG. 8  that 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 in  FIGS. 10 and 11 . 
         [0022]    Conversely, if the comparison of sensing signal SS and reference signal RS indicates the flow of test current I T  through write head  30  is unequivalent to the flow of write current I W  through write head  30  under a normal write condition (i.e., test current I T =0 or is significantly less than write current I W ), then test current sensor  71  generates a test current failure indicator TCF as shown in  FIG. 9  that 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 in  FIGS. 10 and 11 . 
         [0023]    In practice, there are no limitations or restrictions to the structural configurations of a write current driver circuit  50  and an open write condition detector  70  as shown in FIGS.  5  and  8 - 11  in implementing the open write condition detection method shown in  FIG. 7 . To further illustrate an understanding of the open write condition detection method,  FIG. 12  illustrates an exemplary structural configuration of write current driver circuit  50  as a known voltage mode current driving device having a H configuration of a pair of NFETs M 1  and M 2  and a pair of PFETs M 3  and M 4  for selectively applying a voltage source V S  to a DC series resistance/inductance load R 6 /LI of write head  30  via driver card  40  represented by resistors R 3 -R 5  and via cables C 1  and C 2 . 
         [0024]    Also shown in  FIG. 12  is an exemplary structural configuration of open write condition detector  70  employing a pair of test current drivers in the form of a NFET M 5  and a PFET M 6 , a voltage generator having a pair of resistors R 1  and R 2  and a voltage comparator U 1 . FETs M 5  and M 6  are electrically connected in parallel and are electrically connected in series with a parallel electrical connection of resistors R 1  and R 2  that generate a test voltage V T  at an inverting input (−) of voltage comparator U 1 . A programmable reference voltage V R  representative of a flow of write current I W  through write head  30  is applied to a non-inverting input (+) of voltage comparator U 1  whereby voltage comparator U 1  generates a test current indicator TCI based on a comparison of test voltage V T  to a reference voltage V R . 
         [0025]    With this integration, the storage drive operates between an idle mode, a test mode and a write mode in accordance with an operational mode table  100  shown in  FIG. 13 . Specifically, the idle mode of the storage drive encompasses FETs M 1 -M 6  being in non-conductive state (“NONC ST”) whereby write current driver circuit  50  and test current sensor  70  are electrically disconnected from write head  30  as shown in  FIG. 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 M 1 -M 6 . 
         [0026]    The test mode of the storage drive encompasses FETs M 3 , M 5  and M 6  being in a conductive state (“COND ST”) and FETs M 1 , M 2  and M 4  being in a non-conductive state whereby write current driver circuit  50  and test current sensor  70  are electrically connected to write head  30  as shown in  FIGS. 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 M 3 , M 5  and M 6 , and by an application of a disable logic level of gate signals PN, MN and MP to the respective gates of FETs M 1 , M 2  and M 4 . 
         [0027]    The write mode of the storage drive includes FETs M 5  and M 6  being in a non-conductive state with FETs M 1  and M 4  being in a non-conductive state and FETs M 2  and M 3  being in a conductive state as shown in  FIG. 18 , or with FETs M 1  and M 4  being in a conductive state and FETs M 2  and M 3  being in a non-conductive state as shown in  FIG. 19 . This is accomplished by an application of a disable logic level of gate signals POT and MOT to the respective gates of FETs M 5  and M 6  with either an application of a disable logic level of gate signals PN and MP to the respective gates of FETs M 1  and M 4  and an application of enable logic level of gate signals PP and MN to the respective gates of FETs M 2  and M 4 , or with an application of an enable logic level of gate signals PN and MP to the respective gates of FETs M 1  and M 4  and an application of a disable logic level of gate signals PP and MN to the respective gates of FETs M 2  and M 3 . 
         [0028]    For the test mode, a flowchart  110  shown in  FIG. 14  is representative of an open write condition detection method of the present invention. Specifically, a stage S 112  of flowchart  110  encompasses a controller (not shown) providing the gate signals to FETs M 1 -M 6  to transition FETs M 3 , M 5  and M 6  to a conductive state and to maintain FETs M 1 , M 2  and M 4  in a non-conductive state as shown in  FIGS. 16 and 17 . During a stage S 114  of flowchart  110 , test voltage V T  is indicative of a degree of flow of a test current I T  through write head  30 , and compares test voltage V T  to a reference voltage V R , which is representative of a flow of write current I W  through write head  30  under normal write conditions. If the comparison of test voltage V T  and reference voltage V R  indicates the flow of test current I T  through write head  30  is equivalent to the flow of write current I W  through write head  30  under a normal write condition (i.e., test current I T ≈write current I W ), then voltage comparator U 1  generates test current indicator TCI as a test current pass indicator of a logic low level (“0”) as shown in  FIG. 16  that 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 in  FIGS. 18 and 19 . 
         [0029]    Conversely, if the comparison of test voltage V T  and reference voltage V R  indicates the flow of test current I T  through write bead  30  is unequivalent to the flow of write current I W  through write head  30  under a normal write condition (i.e., test current I T =0 or is significantly less than write current I W ), then voltage comparator U 1  generates test current indicator TCI as a test current failure indicator of a logic low level (“1”) as shown in  FIG. 17  that 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 in  FIGS. 18 and 19 . 
         [0030]    Referring to FIGS.  12  and  15 - 19 , resistors R 1 -R 6  and inductor L 1  may 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 V s  is programmable in the range of 3-6 volts in order to change the magnitude of write current I W  and test current I T  by as much as 40-50%. Resistors R 1  and R 2  have a resistance of 200Ω, resistors R 3  and R 5  have a resistance of 100Ω, resistor R 4  has a resistance of 255Ω, resistor R 6  has a resistance of 25Ω, and inductor L 1  has an inductance of 150 nanohenries. As such, reference voltage V R  is in the range of 0.4 to 0.8 volts, preferably 0.6 volts. 
         [0031]      FIG. 20  illustrates a current mode H configuration write current driver circuit that is similar to the voltage mode H configuration write current driver circuit shown in  FIG. 12  with the exceptions of (1) an elimination of resistors R 3  and R 5 , and (2) source electrodes of NFETs M 1  and M 2  being connected to a current source I S  instead of ground. Current source I s  may be programmable in a typical range of 10 to 50 milliamps in order to change the magnitude of write current I W . 
         [0032]      FIG. 21  illustrates an embodiment of a magnetic tape recorder or tape drive system  120  incorporating an open write condition detector (“OWCD”)  200  of the present invention. A tape drive controller  122  provides a motor control signal to rotate tape reels  124  and move magnetic tape  123  across the read/write transducer head  121 . Read/write channel  125  transmits read/write signals between the read/write transducer  121  and the controller  122 . The data is communicated through I/O channel  129  with host  131 . Lateral positioning of the transducer  121  with respect to the tape  123  is accomplished by positioning actuator  127 . The lateral repositioning is required to access the various tracks of the tape  123  with the transducer  121 . A servo system may be employed for accurate lateral repositioning of the transducer  121 . An exemplary servo system includes a servo detector  126  to detect both the track that the head is currently on and whether the head is off center. Controller  122  indicates the track address of a desired new track to position error detection controller  128  for repositioning the head. Servo detector  126  indicates the current track to position error detection controller  128 , and the controller provides a servo position error signal to positioning actuator  127  which repositions the transducer  121  to the new track. The servo system also provides track following signals to positioning actuator  127  so that the tracks on tape  123  may be closely spaced. Controller  122  uses logic control signals at Power on Reset to activate detector  200  whereby, upon a detection of an open write condition, controller  122  will report a RAS error to thereby flag a need for drive  200  to be serviced or replaced. 
         [0033]    Referring to  FIGS. 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 throughout  FIGS. 5-20 . 
         [0034]    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.