Diagnostic testing apparatus and method

A peripheral system including a microprogrammed processing apparatus coupled to a data processing system and to at least one magnetic tape peripheral device for reading and recording on a multichannel magnetic medium successive bytes of digital signals in blocks, each block having a predetermined format, sad microprogrammed processing apparatus comprising:

• an addressable control store for storing microprograms used to perform said reading and recording of said bytes of digital signals, said store including addressing means and a plurality of storage locations for storing a plurality of basic test routines including a recovery routine for verifying that said processing apparatus can recover reliably said digital signals read from said medium, said recovery routine including microinstructions containing a limited number of constants representative of initial patterns and predicted results;
• decoder means coupled to said control store for generating control signals in response to decoding microinstructions read out from said control store;
• data recovery means operatively coupled to said decoder means and to said peripheral device for assembling into bytes said digital signals transferred by said device at a specified rate for transfer to said data processing system, said recovery means including;
• a plurality of recovery error indicator storage circuits operative to monitor said transfer for generating signals indicative of the occurrence of error conditions during the assembling of said digital signals;
• input means coupled to said control store addressing means, said input means being operative to receive an input signal for conditioning said addressing means to cause said control store to branch to said basic test routine microinstructions;
• control transfer means coupled to said decoder means, to said store, to said device and to said data recovery to control signals from said decoder means during execution of microinstructions of said recovery routine to condition said data recovery means for receiving only groups of digital signals generated from said initial patterns and inhibiting transfers of said digital signals from said device;
• and,
• logic means coupled to said control store and to said plurality of indicator storage circuits, said logic means being conditioned by control signals from said decoding means to compare the states of said recovery indicator storage circuits with a pattern of signals received from said control store representative of the predicted states of said recovery indicator circuits as a result of applying said groups of digital signal patterns of a first block to said data recovery means for determining that said data recovery means is operating reliably.

A peripheral controller coupled to a data processing system and to a plurality of magnetic tape devices operative to read and record frames of digital signals arranged in blocks on a multichannel magnetic medium, each block having a predetermined format, said controller including an addressable control store for storing microprograms used to perform said read and write operations, decoder circuits coupled to said control store for generating control signals in response to decoding microinstructions of said microprograms, a processing unit for performing arithmetic and logic operations upon a pair of operands, a data recovery unit and for assembling into bytes, digital signals transferred by said selected device at a specified rate for transfer to said date processing system, said recovery unit having an input coupled to receive digital signals from a selected device and an output coupled to said processing unit and including a plurality of recovery error indicator storage circuits operative to store signals indicative of error conditions occurring during the assembling of said digital signals received from said device, said controller further including self-testing apparatus comprising:

• selector circuit means having an output and at least first and second inputs, said output being coupled to said input of said data recovery unit, said first inputs being coupled to said input of said selected device and said second input being coupled to said processing unit;
• a first storage means operatively coupled to said data recovery error indicator storage circuits for storing signals indicative of error conditions detected by said recovery unit;
• said control store including input means for receiving an input reset control signal from said data processing system and further including a plurality of basic test routines, one of said routines for verifying that said data recovery unit is operating properly, said one of said routines including a limited number of microinstructions containing constants corresponding to initial patterns and expected results patterns, said control store being responsive to said reset signal to branch to said basic test routines, said decoder circuits being conditioned by a first microinstruction sequence of said one routine to generate signals for conditioning said selector circuit means to connect said recovery unit to receive signals only from said second output and said decoder circuit being conditioned by repeated execution of other microinstructions of said one routine to generate signals for conditioning said processing means to generate digital signals of a first block from said initial patterns arranged in said predetermined format and said decoder means being conditioned by a sequence of test microinstructions upon completion of assembling into bytes said digital signals of said first block to generate signals to compare the states of said first storage means with one of said patterns of expected results for testing whether said recovery unit is operating reliably.

An improved method of initializing a magnetic tape peripheral subsystem in response to a control signal from a data processing system coupled to said peripheral system, said peripheral system including a microprogrammed input/output magnetic tape controller coupled to a plurality of magnetic tape devices for reading and recording on a multichannel medium successive bytes of digital signals in blocks, each block having a predetermined format, said controller including a control store for storing microprograms used for reading and recording said bytes and a data recovery unit coupled to receive signals from a selected one of said devices and assemble said signals into bytes for transfer to said data processing system, said recovery unit including a plurality of error indicator storage circuits for signaling the occurrence of error conditions during the assembling of said bytes, said improved method including the steps of:

• storing in said control store a plurality of basic test routines, one of said test routines involving microinstructions containing constants representative of initial patterns used to generate groups of digital signal patterns which constitute blocks arranged in said predetermined format and patterns representative of expected results for verifying that said controller can recover reliably said signals from said medium;
• generating signals by said controller in response to said control signal which conditions said control store to branch to said one of said test routines;
• generating signals in response to microinstructions of said one of said test routines for connecting said data recovery unit to receive said generated groups of digital signals and inhibiting transfer of digital signals from a selected one of said plurality of magnetic tape devices;
• generating said groups of digital signals from microinstructions containing constants representative of said initial patterns and applying them to said recovery unit;
• monitoring the states of said error indicator storage circuits in said controller during the application of said groups of digital signals;
• comparing a predetermined one of said patterns obtained from one of said microinstructions read from said control store indicating said expected results with the states of said error indicator storage circuits;
• and
• signaling that said recovery unit is operating reliably in recovering said groups of digital signals when the states of certain ones of said indicator storage circuits indicate that said blocks applied to said recovery unit contain patterns of digital data signals representative of uncorrectable error conditions as defined by said predetermined one of said patterns.