Abstract: A programmable menu driven qualifier designed to make the abstract nature of small computer system interface (SCSI) definition easier to understand and work with. The qualifier is intended for testing and evaluating direct access and sequential access SCSI devices, such as disc drives and tape drives connected to the qualifier by an SCSI bus, the testing being carried out in accordance with ANSI SCSI-1 and ANSI SCSI-2 definitions. The qualifier is completely menu driven, and all commands are executed with a single keystroke of the keyboard. The qualifier uses a simple built-in concept which allows an operator quickly to become familiar with an SCSI protocol and command structure.

Abstract: A unity power factor power supply which includes a boost converter connected to the alternating current line which is controlled to draw sinusoidal current from the line by operating as a current regulator having a current reference control signal which tracks the line voltage waveform, thereby to minimize the required input current for a given power output.

Abstract: A programmable servo pattern generator for use in a magnetic disc drive servowriter system. The servo pattern generator of the present invention stores a multiplicity of different servo patterns in a convenient user-oriented format, and it provides high frequency pulse trains of NRZ data representing the different servo patterns. These different servo patterns are derived from the pattern generator of the invention as required and in the particular formats to be written into the magnetic disc drives of the same or different manufacturers.

Abstract: A portable servowriter system for writing a closed clock track and servo tracks on one or more of the fixed discs of a fixed disc magnetic disc drive without the aid of a mechanical head positioner; and which is also capable of writing a closed clock track and servo tracks (either on a dedicated disc surface or of the embedded form) on one or more of the discs of a rotating disc magnetic disc drive with the aid of a mechanical positioner.

Abstract: A portable, programmable, microprocessor-controlled, universal field test unit is provided which is capable of performing functional tests on most, if not all, of the better known present-day disc drives, including the 80, 160 and 300 megabyte types. The unit to be described will be termed herein as a programmable disc drive qualifier, and it is capable of carrying out a wide variety of special test programs, as well as standard diagnostic programs, and it may also be used to format disc packs with many different formats, including thirty-two and eighty-six sector formats. The qualifier may be internally set to count all data errors, or only uncorrectable errors. The qualifier, in the embodiment to be described, is controlled by a combination of twelve operation keys and twelve numeric keys. A complete instruction is generated by the actuation of one of the operation keys and one of the numeric keys. Individual instructions may be executed in the unit, or it may be run automatically under program control.