Multiband automatic test equipment-a computer controlled check-out system

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1 Multiband automatic test equipment-a computer controlled check-out system by TERUHISA KURODA McKinsey & Company, Inc. New York, New York and THOMAS C. BUSH Sanders Associates, Inc. Plainview, New York INTRODUCTION The major problem facing organizations using electronic devices is in test and maintenance of the equipment. Due to the high cost of the equipment and demands made o~ its maximum utilization, fast and reliable testing procedures are required to minimize downtime for repair and calibration. The purpose of this paper is to describe the computer and software system developed for MATE, the Multiband Automatic Test Equipment. The MATE System was developed to test naval avionic equipments. Information related to these naval avionic equipments is both "classified" and irrelevant to the MATE systems in the software sense and, therefore, is not included in this paper. SYSTEM OVERVIEW The MATE System is self-contained and consists of all software and hardware necessary for its operation. Basic processes in the use of the MATE System are shown in Figure 1. The test engineer first performs the necessary analyses to determine what tests must be made on a particular device; These tests are then organized by a 3-digit test-sequence number with a 3-digit test-series number. These tests are then flow charted and coded, taking into account the rules of the MATE programming language. Since this programming language is English-like, programs are called English Language Programs or ELPs. ELPs are punched on paper tape and catalogued on the disk, unit under test is connected to MATE; and tests are performed. Figure 2 shows the components of the MATE System from the programming point of view. It shows how major programs such as the Executive Program, Language Processor, and Utility Programs interact with various input-output devices in the system. Measuring devices and stimuli-generating equipment appear as input-output units. The use of pertinent data on the disk such as indices, tables, and libraries have been indicated. Hardware connections are shown in Figure 3. These connections are ra"ther straightforward, except for the use of two busses to transfer data between test modules and the computer. The address bus is used to send the device address of the test module to be referenced in the input-output operation. Data from test modules are sent across the data bus. Execution of tests is shown by Figure 4. It shows how various data stored on the disk are used. The picture of the MATE station is shown in Figure 5. It can be seen how compact and self-sufficient the system is. MANUAL CHECKPOINT INADEQUATE The basic testing process consists of sending a simple stimulus to the unit under test, receiving the resulting response, and measuring the response against a standard. As the complexity of the devices to be tested increases, there is a corresponding rise in the number and interrelationships among stimuli and responses. The traditional manual testing approach, with the use of lash-ups and semiautomatic control devices, is totally 451

2 452 Spring Joint Computer Conference, 1971 CONNECT UNIT TO BE TESTED CATALOGUE ELPON DISK ENGINEERING ANALYSIS OF TESTS EXECUTE TEST CODE TEST INTO ELP ORGANIZE TESTS BY TEST SEQ. AND SERIES FLOW CHART TEST come possible to build a computer-monitored automatic check-out system. The MATE System is a self-contained test station consisting of test equipments, computer, and operator control stations. This system can be driven in automatic mode by the computer or in manual mode by paper tape or operator action. The manual mode of operation is not described, since it does not require the computer, and, therefore, is not relevant to this discussion. In the automatic mode, the MATE test station is driven by English Language Programs (ELP), written by test engineers and catalogued on disk storage, which is operated upon by the MATE software. The test process is directed by the operator who can intervene and override any preplanned sequence of test or parameters. The MATE System was designed in a modular fashion to facilitate modification and/or growth. Additional stimuli generators and measurement devices can be accommodated by adding new programs to the MATE software. New units under test, sequence of test or test parameters can be incorporated by writing new ELPs. The MATE System, compared to manual methods, will: Figure I-MATE process chart inadequate for testing avionic equipments because of the: Large amount of time spent in testing Inherent errors introduced in a manual process Shortage of required personnel and number of test stations to serve testing needs within a time period Tedious method of locating faults Inaccurate method of recording test performance. Reduce check-out time Apply a uniform test standard to units under test Reduce the number of check-out personnel Reduce training time for personnel Record test results on hard copy Decrease errors introduced by operator AUTOMATED SYSTEM IS THE ANSWER With the declining cost of computers and peripherals, and emergence of analog-digital technology, it has be- Figure 2-MATE system components Figure 3-Hardware connections

3 Multiband Automatic Test Equipment 453 Reduce skill level required of operator Isolate faults to a level suitable for further manual tests Permit the engineer to direct testing procedures via an easily usable test language Reduce the number of test stations required to handle the same load under a manual process. HARDWARE DESCRIPTION The hardware of the MATE System consists of a computer, various test modules and a control/display panel. These system components appear like any other I/O device to the computer. Thus, the MATE hardware operates a computer with many I/O devices. Computer configuration Varian 620/i computer 8192 word storage (16 Bit word) KSR-33 Teleprinter 131K words of disk storage 200 char/sec paper tape. Test modules Figure 5-MATE station Testing Operations OPERA TOR LOADS AND EXECUTES A BOOTSTRAP PROGRAM. WHICH CALLS CORE RESIDENT PROGRAMS FROM DISK STORAGE OPERATOR DIALS UP THE DESIRED TEST SERIES AND RELATED PROGRAM VIA THE CONTROL PANEL Disk. Storage A test module is an electronic test instrument or stimulus generating device such as digital voltmeter or a sine square generator. These modules must all appear as similar devices which can: Communicate with the computer by digital word transfer Convert digital information to analog signals Convert analog measurements to digital for transfer to the computer Respond to and activate discrete signals for system control functions Respond to strobing by a unique device address. TESTS ARE EXECUTED. OVER LA Y MODULES ARE CALLED FROM DISK STORAGE ACCORDING TO THE ELP STATEMENTS ENCOUNTERED DURING EXECUTION Testing Terminated LANGUAGE PROCESSOR OVLY NO.1 OVLY NO 2 OVLY:NO.3 OVLY NO. (N) * UTILITY PROGRAMS CATALOGUE SOURCE CATALOGUE OBJECT LIST DISK STORAGE TEXT EDITOR Typical test modules contain the following features: Modular packaging Built-in self-test circuitry which continuously monitors the module outputs for failure Control p~nel programmed response indicators Manual or automatic operation Control panel alignment and self-check output. Control panel * Indicates Programs Not Required for Testing. Figure 4-Test organization From the standpoint of the operator/user, the control panel is the central point of all testing activities. Consequently, the control panel was designed to accom-

4 454 Spring Joint Computer Conference, 1971 modate the testing needs of the operator. It has no controls related to the computer. From the control panel the operator can: Initiate tests by retrieving and executing ELPs stored on the disk Override any faults which may be encountered while executing tests Repeat any test Repeat any measurement Interrupt the testing sequence, manually alter any of the test parameters and continue testing Acknowledge testing results (GO/NOGO, run, etc.) Execute testing ELPs one instruction at a time Reset the entire system. Display panel The English elements of the MATE language consist of verbs (test actions), test module names (nouns), parameters (adjectives), and units of measure (other adjectives). In order to reduce errors in coding, all English words can be used in either abbreviated or full form. Abbreviations require using only the leading characters required to make the word unique. For example, the word "calibrate" can be expressed as CA, "step attenuator" as STEPAT, "RF band" as RFB, etc. List of verbs The verbs III the MATE language consist of the following: MATE-VERB ACTION TABLE The display panel, although not a control function, is physically located adjacent to the control panel and contains all the visual displays required in testing. The panel can display: Test number currently being performed Operator instructions (i.e., operator decision, etc.) Next ELP instruction step to be executed (when in single step mode) Alarm indications to alert the operator of hardware malfunctions. Condition of I/O RF switching paths via an indicator lamp matrix Test results and values Indications and/or displays provided by the unit under test. MATE PROGRAMlVIING LANGUAGE ELP Delimiters Input/Output Decision Subroutines Computation Branch Function of verbs BEGIN TERMINATE READ DISPLAY SETUP CALIBRATE UPDATE LOOKUP WAIT FOR SYSTEM RESET IF PERFORM DEFINE END LET GOTO The MATE programming language is a specialpurpose language designed for use by test engineers. Since its format is cryptic English, we refer to it as ELP (English Language Programs). Familiar engineering expressions are retained while introducing some necessary programming concepts like "go to" and "execute subroutine." Th~ languag~ is easy to learn and requires no previous knowledge or exposure to programming. The basic element of the language is a statement. An ELP statement takes the following skeleton format with the contents depending on the verb: Statement number Verb Contents. Each verb in the MATE serves specific functions and requires certain information as described in the following: ELP delimiters The BEGIN and TERMINATE verb serves to define the start and end of a test sequence. It is identified uniquely by.a 3-digit test-series and 3-digit test-sequence number. Input output verbs The following verbs perform I/O operations to the teleprinter, disk, test modules, control panel, or display panel.

5 Multiband Automatic Test Equipment 455 The SETUP verb is used to send stimuli to the test module and the READ verb is used to obtain the resultant response from the test module reflecting a test made on the unit under test. The DISPLAY verb is used to display information on the teleprinter or display panel. Symbol tables are referenced by the UPDATE and LOOKUP verbs. These verbs are I/O related since symbol tables are stored on the disk. The WAIT FOR verb is used to wait for the occurrence of hardware responses. Such as I/O complete or test module ready interrupts, and operator action like a Go /NOGO decision. The SYSTEM RESET verb is used to initialize all test modules. Examples of I/O verbs are: 001 SETUP, STEP ATTN (ATTN =59 DB) 002 READ, PWR OUT METER 003 DISPLAY, MESSAGE ('VOLTS', C, K, LOLIM) 004 UPDATE, TABI ('LAB!') 'INC' 005 LOOKUP, TABI ('LABI') 006 WAIT FOR, RESUME 007 SYSTEM RESET 008 CALIBRATE, AUTO LEVEL (FREQ= 'LABL') Decision The IF verb is used to ask the true-false question based on the mathematical expression greater than (> ), less than ( <), equal (= ), greater than or equal to ( ~ ), and less than or equal to (::::;). If the answer is true, a jump is made to the specified ELP statement number. A false answer will cause the execution of the next sequential ELP statement. An example of the IF verb is: 010 IF, (2.5)::::; 'LABEL' < (3.0), GOTO (S100) Subroutines Subroutines can be included in the ELP provided they are defined at the beginning by the DEFINE verb and at the end of the END verb. The DEFINE verb is used to list those parameters in the subroutine which can be varied by the calling program. The execution of a subroutine is done via the PER FORM verb. It can also deliver values for parameters of the subroutine. For example: 010 PERFORM (SI00) (33.25) 100 DEFINE ('X') 101 LET, 'X'='X' END Computation Computation is indicated by the verb LET. Operators available are add (+), subtract (-), multiply (*), divide (/), and exponentiate (i ). Any mathematical expression can be stated, using these operators. The interpretation of the expression is in left-to-right order. Examples are: Branch 020 LET, X=A i B+CX 030 LET, X=A+B/C A branch in the ELP is accomplished by the use of the GOTO verb. The destination can be specified as an ELP statement number, a new test sequence number, or a work indicating the end of a test series. Examples of the GOTO verb are: 100 GOTO, (S200) 200 GOTO, (TI25) 300 GOTO, (EXEC) SOFTWARE DESCRIPTION After a survey of the computers which could be used in the MATE System (in terms of size, cost, and system requirements), the Varian 620i was selected. The Varian 620i, being a mini-computer, has software and peripheral equipment which is either too general or too specialized for a given application. Often I/O devices, such as high-speed tape readers, are made by different companies and frequently require special interfaces to the computer. Thus, what could have been an applications programming task explodes into a major software development project. Further burden is imposed by the sparcity of mini-computer simulators. Software development, therefore, must be done directly on these computers which have only limited debugging aids. The MATE System was no exception. The software developed included: Executive program Input/Output handler for disk, high speed tape reader and teleprinter

456 Spring Joint Computer Conference, 1971 MATE software (object program) catalogue and maintenance routines English Language Program (ELP) catalogue and maintenance routines Utility programs to

6 456 Spring Joint Computer Conference, 1971 MATE software (object program) catalogue and maintenance routines English Language Program (ELP) catalogue and maintenance routines Utility programs to print contents of core and disk storage Mathematical package to perform programmed floating point arithmetic, exponentiation, and data format conversion Interpreter program to operate upon ELPs Test module simulator. MATE LANGUAGE PROCESSOR Test procedures written by the engineers in the MATE language must be translated into machine instruction for execution. A detailed tradeoff analysis was conducted to resolve the question of off-line compiler application versus the on-line interpreter/compiler technique for the MATE System. The interpreter approach was chosen for the following reasons: Reasonable timing requirements by test equipment Engineers could work with the MATE language for programming, execution, and maintenance, without learning the computer machine instructions Due to limitation of external storage, there was no room to maintain both ELPs and software programs on the disk Quicker implementation of the total MATE System Ease of modification for extension of MATE language Ease of maintenance of operating system. The MATE language processor is an interpreter. It consists of a resident and overlay programs. The resident part contains a floating poirit mathematics package, data format conversion programs (i.e., ASCII to binary, floating point to binary, etc.), and the general processor to identify, validate, and parse a source statement to be executed. When the ELP verb is identified, an appropriate overlay program will be invoked to interpret and execute the ELP statement. Executive program The executive program is the center of the MATE System. It is responsible for bringing together the operator, language processor, test modules, and test programs. The executive program is resident in core memory. The main components are: Interrupt processor Input/Output handler Table lookup routines Startup-shutdown routines Test program statement monitor. The interrupt processor handles three types of interrupts: input-output alarm stop, and manual override stop. Input/Output interrupts are caused by operator action on the control panel, input data have arrived from test modules, or ready state reached by test modules. When an alarm condition occurs on test modules, the alarm stop interrupt occurs. The computer stops and the system cannot be restarted until the alarm condition is reset. The manual override interrupt occurs whenever the test module, indicated on the control panel for manual intervention, is addressed. The computer remains in the wait state while the operator performs the necessary manual action on the control panel. The system is restarted when so directed by the operator. The Input/Output handler performs all the Input/ Output for the system. Devices handled are test modules control panel, display panel, teletype, and disk storage. In all cases, the calling program provides a parameter list which provides all the data to perform the physical input-output operation. There are two types of I/O operations for test modules and control panel. They are output pulse signal and data transfer. The output pulse signal is used to activate control panel lights and to describe the data about to be sent to test modules. Data transferred to test modules is in multiples of computer words and is either a device address or information word. I/O for the disk storage and teletype is done by a specified number of words or to a control character terminating the record. For disk I/O, the physical track address must be specified. Since there is no wait state in the computer, the read from teletype instruction sequence is used to simulate a wait state when soliciting interrupts. Due to the shortage of core storage, all tables are stored on the disk. These tables hold information relating to global and local symbols and their computed values, and calibrated standards referenced by test processes. Local symbols are symbols used only within a test sequence. Those symbols which are used among test sequences within test series are defined as global symbols. The local symbol table is reset at the beginning of a new test series. The test module simulator is an important part of the

7 Multiband Automatic Test Equipment 457 Executive Program. It permits the MATE System to be checked out without test modules. The teletype simulates the test modules. Inputs, described in octal code, are typed in by the operator and outputs are similarly printed. The simulator was invaluable in locating hardware-software problems and faults in test modules. The startup-shutdown routines control initialization and termination procedures. At startup, the test series and test sequence numbers supplied by the operator, via the control panel or teletype, are validated. The appropriate ELP is located. Global and local tables are initialized. The language processor is called to begin interpreting the test ELP program. Shutdown simply involves readying the system for another test. The test program statement monitor allows operator control of the current statement being executed. Control panel optious permit displaying the current statement number on the control panel, executing one statement at a time, repeating a given test sequence, restarting a test sequence from the last measurement read, or inhibiting entry into fault isolation program in case of errors. This monitor allows the operator to control the execution of a test statement at the source language level from the control panel and away from the computer. Utility programs An integral part of the MATE System are the utility programs. These programs consist of elementary routines such as core and disk dump programs, and comprehensive disk data handling programs. Disk service programs maintain software programs and ELPs on disk storage. Further, they condense indices and data storage areas automatically when gaps develop as a result of deletions. As both a startup and backup procedure, all data stored on the disk are stored on paper tape. There is an initialization program to set up the disk storage and a bootstrap program on paper tape to begin a test process. CONCLUSION The MATE automatic check-out system which has been described, has been in operation for more than 6 months. Its performance has given support for a bright future in computer-driven check-out systems. The MATE System has demonstrated that: Test time can be reduced by a factor of 20 over manual methods It is economically and operationally feasible to use mini-computers in automatic check-out systems. Test engineer without previous programming experience can learn to write test programs in the specialized programming language, like the MATE language, in 2 days. REFERENCES A guide to atlas for test specification writers ARINC Report 418 Aeronautical Radio Inc Annapolis Maryland May

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