Abstract: An automated storage system uses a pass-through picker assembly interposed between a storage device and a plurality of storage cells, wherein the pass-through picker assembly is mounted on an accessor and incorporates independently operating fore and aft grippers driven by a single motor. The fore and aft grippers are tandemly mounted such that the fore gripper can be aligned to one of a plurality of storage cartridges located with the storage cells, and the aft gripper can be aligned with a storage slot of the storage device. The pass-through picker design allows the fore gripper to grasp a storage cartridge, feed the cartridge through to the aft gripper, release, and then allow the aft gripper to grip and pass the storage cartridge to the storage slot. In this way, a special priority cell of the storage cells, directly across from the storage slot, can very quickly pass a priority storage cartridge directly to the storage device without moving the pass-through picker assembly.

Abstract: An optical drive provides an internal routine for automatically optimizing the common mode rejection ratio of the magneto-optic data output signal. A microprocessor provides control to a controller module which in turn supplies a plurality of calibration signals to a data detecting portion. The calibration signals modify predetermined parameters of the data detecting portion based upon measuring a predetermined parameter indicative of the common mode rejection ratio. The common mode rejection ratio optimization corrects for mismatches in both the optical elements and in the electronic data circuits.

Abstract: A method and apparatus which first calculates track to track skew in a tape device and then uses the results of that calculation to adjust the windows for detection of sync and resync characters. The system makes use of global circuitry which adjusts the sync and resync windows for all tracks based upon the skew calculation. In the case of the windows used for detecting resyncs, when skew is determined to be large, the global resync window must span a larger time period to account for the skew in detecting resync marks. Conversely, when there is little or no skew present, the windows for resync detection can be narrowed. Normally, the track logic utilizes its own local windows to detect resyncs. If a track misses a resync, however, it must use the global resync window to determine the next resync location. Once the tracks are resynchronized, control can return to local track circuitry to maintain synchronization.

Abstract: A method for servicing a mount request in an automated storage library in which all of the peripheral storage devices therein are occupied and which permits an active data storage medium to be temporarily demounted and subsequently remounted in any subsequently available peripheral storage device is disclosed. To service a mount request requiring that a data storage medium be demounted, the access information for the data storage medium to be demounted is first retained. After demounting and servicing of the mount request, the retained access information is used to permit remounting of the previously mounted data storage medium in any subsequently available peripheral storage device, thereby minimizing the risk of delay in remounting. The method also allows for optional parameters to prevent temporary demounting in an automated storage library, or to prevent temporary demounting of particular data storage media. An automated storage library and program product employing the method are also disclosed.

Abstract: A robotic manipulator for picking and placing data storage cassettes in an automated storage library. The manipulator has a pair of fingers, one finger being longer than the other. An eject bar is located between the fingers and has a tab for pushing a storage cassette into the seated operative position in an IBM 3480 type tape reader. The manipulator approaches the slot in the reader, supporting the data cassette on the long finger and holding it in place with the short finger. The short finger pivots to free the cassette and the eject bar pushes it into the reader. When the eject bar is clear of the long finger it pivots downwards so that the tab engages the top of the cassette and pushes it into the seated position in the reader.

Abstract: A method and apparatus which first calculates track to track skew in a tape device and then uses the results of that calculation to adjust the windows for detection of sync and resync characters. The system makes use of global circuitry which adjusts the sync and resync windows for all tracks based upon the skew calculation. In the case of the windows used for detecting resyncs, when skew is determined to be large, the global resync window must span a larger time period to account for the skew in detecting resync marks. Conversely, when there is little or no skew present, the windows for resync detection can be narrowed. Normally, the track logic utilizes its own local windows to detect resyncs. If a track misses a resync, however, it must use the global resync window to determined the next resync location. Once the tracks are resynchronized, control can return to local track circuitry to maintain synchronization.

Abstract: Two identical CRC circuits are cross coupled to make alternate CRC calculations based on the other CRC circuit's calculation. Throughput of the CRC code calculation is improved by applying alternate input data simultaneously at each of the CRC circuits so that when one calculation is completed the next input data is available to immediately begin the next calculation. The output of each CRC circuit is fed into one of two latches that make up an LSSD register such that the first latch captures the first CRC calculation on a first clock of non-overlapping clocks. The second CRC calculation is captured by the second latch on a second clock of the non-overlapping clocks. Two CRC calculations can be made in one period of the non-overlapping clocks while avoiding race problems.

Abstract: A power amplifier supplies substantial load currents that must be accurately monitored to provide feedback so that the load currents can be properly controlled. A sense current is generated from a load current that is scaled such that the sense current is an accurate representation of the load current but having a substantially smaller magnitude. The scaled sense current is generated by coupling a power sense resistor to a pilot sense resistor by a voltage follower. The power sense resistor is in series with the load current and develops a load voltage thereacross. A sense voltage, being substantially equal to the load voltage is impressed at the pilot sense resistor by the voltage follower. The pilot sense resistor is some predetermined ratio of the power sense resistor so that absolute values are not critical. The sense current flowing through the pilot sense resistor is therefore scaled according to the ratios of the power and pilot sense resistors.

Abstract: A method for efficiently utilizing data recording media in a data processing system performing data compression beneath the level of the host processor is disclosed. To improve the ability of a recording media to be copied without increasing host processor overhead, the control unit which sees the compressed data is checked only upon recording a predetermined amount of uncompressed data. At such time, a compression ratio is calculated for the current data set and is used to monitor the recording of the remaining data of the current data set in compressed form. When a predetermined amount of compressed data is estimated to be recorded, the predetermined amount being the minimum storage capacity of a recording media, recording begins on a new recording media.

Abstract: A dual sense non-differencing peak detector locates a peak without introducing unwanted noise components, and also corrects for signal asymmetries. This is accomplished by identifying two sequential sets of two successive samples each. The first set includes samples that fall on each side of a threshold voltage on the rising edge of the signal. The second set includes samples that fall on each side of the threshold on the falling edge of the signal. For each of the two sets of samples, the point at which the signal substantially equals the threshold is found by interpolation. The two threshold points, for a symmetrical signal, fall equidistant from the peak, and hence the peak is easily located as being equidistant therebetween.

Abstract: Reliability of an automated storage library is improved by mounting at least one CCD cameras on a turret plate with two grippers, wherein the CCD camera provides video support for both grippers. The turret plate is rotatably mounted on the end of an anthropomorphic robot arm such that the camera and each gripper is rotated and angled into position as needed for viewing or gripping, respectively. The CCD camera is positioned to view a tape cartridge for capturing an image of the label attached thereto. While the captured image is being processed to verify the VOLSER, the first gripper is rotated into position and moved forward to grip the desired tape cartridge. The robot arm them moves the camera and gripper assembly to a tape drive and rotates the second gripper into position to remove another tape cartridge from the tape drive. The turret plate is again rotated to position the first gripper for inserting the verified tape cartridge into the tape drive.

Abstract: The present invention locates spare sectors for replacing secondary defects found during disk use. A sorted defective sector list is maintained for tracking the spare sectors that have been previously used for replacements of other secondary defects. When a secondary defect address is found, a secondary defect list is updated both on the disk and in the drive's memory. A spare sector, for replacing the secondary defect is located by first calculating a group number to determine which group the secondary defect is located in. Next, the boundaries for a plurality of spare sectors allocated for that group is determined. After searching the replacement sector list, the first available spare sector of the plurality of spare sectors is identified as the replacement sector. If all of the plurality of spare sectors have been previously assigned as replacement sectors, a spare sector is instead located from a plurality of spare sectors allocated to a neighboring group.

Abstract: An apparatus for efficiently utilizing data recording media performs data compression beneath the level of the host processor is disclosed. To improve the ability of a recording media to be copied without increasing host processor overhead, the control unit which sees the compressed data is checked only upon recording a predetermined amount of uncompressed data. At such time, a compression ratio is calculated for the current data set and is used to monitor the recording of the remaining data of the current data set in compressed form. When a predetermined amount of compressed data is estimated to be recorded, the predetermined amount being the minimum storage capacity of a recording media, recording begins on a new recording media.

Abstract: An adjustable near unity power factor is achieved while reducing harmonics in a switch-mode power supply by replacing the conventional diode bridge in the front end with an H-bridge driver. Two feedback loops are required, one feedback loop is used to regulate a DC bulk voltage by comparing the DC bulk voltage to a reference voltage and generating an error signal therefrom. A programmable offset is applied to the error signal for adjusting the power factor. A second feedback loop samples and scales the AC input voltage for use as a scaled replica of the input current. The actual input current is then compared to the scaled replica current to produce a second error signal. The two error signals are multiplied to determine the desired input current wherein the desired input current follows the AC input voltage. The desired input current is pulse width modulated by a fixed frequency sawtooth waveform for providing switching signals for controlling the H-bridge driver.

Abstract: A memory fault mapping apparatus detects faults generated in a memory array during on-line operation. As the memory array is randomly accessed, single bit error are detected, corrected, and mapped into an error memory. The errors may be mapped in an error memory having a memory location for each memory of the memory array or alternatively, by grouping memories together and when the errors generated by any one group exceeds a predetermined threshold of errors, testing only the memories in that group off-line. By grouping the memories a substantial reduction in the amount of error memory required can be achieved. A SEC/DED syndrome generator detects single and double bit errors, correcting the single bit errors while providing an indication of which memory generated the error. An error memory stores error counts for the memory array, each error count indicating the number of errors for a specific memory or a group of memories.

Abstract: A data clock is synchronized to a modulation coded signal read from a moving storage medium by a phase error estimator circuit that samples the modulation coded signal two times on each side of a detected peak. A first detected data bit taken at a time N- 2 (two time periods prior to the detected peak) is used to predict the expected value of a first modulation coded signal sample taken at a time N- 1 (one time period prior to the detected peak). Similarly, a second detected data bit taken at a time N+ 2 is used to predict the expected value of a second modulation coded signal sample taken at a time N+ 1. Because the first and second detected data bits are able to predict the first and second samples, respectively, the phase error estimator circuit is able to accurately detect phase errors when sampling arbitrary data as would be presented by a (1,k) modulation coded signal. The expected values at times N- 1 and N+ 1 are compared to the actual values and error voltages are determined therefrom.

Abstract: Improved conversion efficiency and lower output ripple are achieved by a DC-to-DC converter that uses an H-bridge driver to alternately energize first and second inductors. By alternately energizing the first and second inductors, a higher switching frequency can be maintained allowing for the use of smaller inductors while reducing ripple in the output voltage. The reduced ripple in turn reduces the need for filtering. Additionally, the first and second inductors are wound about a common core such that a mutual inductance exists therebetween. The mutual inductance results in trapezoidal currents in each inductor instead of the typical sawtooth waveforms. This results in still lower ripple in the output voltage.

Abstract: An interleaved head for reading and writing data transitions onto a magnetic tape. A magnetic recording system for the bi-directional transportation of the tape media across the interleaved head. A controller controls the tape drive in a reel-to-reel format to accomplish the bi-directional motion of the tape media. The interleaved head includes two modules with each module having a plurality of alternating read and write transducers alternately spaced apart along a single line placed transverse to the movement of the magnetic tape. The two modules are placed together such that the write gaps of one module are aligned with the read gaps of the other module. Each read module includes the magneto-resistive element. Each write transducer includes a thin film conductor driving a nickel zinc ferrite substrate as one pole piece and a nickel zinc closure piece as the second pole piece.

Abstract: A method for dispatching work requests in a data storage hierarchy in which directory data is promoted in variable length spans, the use of which are maximized even for work requests entering the work request queue after the span is chosen, is disclosed. A queue of work requests is initially scanned to determine if any requests therein require access to directory data stored in secondary storage within a prescribed proximity of that required by the next request to be dispatched. If such other work requests exist, then directory data in addition to that required by the next request to be dispatched is also promoted. To minimize seek time and rotational latency, the additional data is promoted from secondary storage in a single device I/O cycle. The additional data is chosen by adjusting the outer limits of the span as each work request in queue is scanned. After the actual promotion of the span of data, the existing work request is completed.

Abstract: An improved method of tracing the paths used in execution of a computer program is disclosed. The method includes using the state of a single bit to denote the referencing of a trace point in the program. The trace points are logically located near the program branch points. One or more bit maps are arranged in a known state at the beginning of program execution and the state of a particular bit in one of the bit maps is set when the associated trace point is referenced. Each bit is associated with a particular trace point according to its position in the bit maps. After program execution, the bit maps are compared to the source listing to determine which trace points were referenced. The use of single bits to denote the referencing of trace points minimizes the degradation of performance efficiency of the target program.