JPH05264657A - Scanner path assigning system - Google Patents

Abstract

PURPOSE: To perform a test practically independent of hardware by providing a scanner driver for operating a scanner in response to a test program which can operate the configuration of a scanner system. CONSTITUTION: An automatic circuit tester 10 comprises a memory 29 storing a test program for specifying the connection being made between the driver/ detector 14 or the wave generator 16 in a tester 10 and a device 12 to be tested without specifying the state of scanner making these connection with respect to the terminal of an instrument and the test point of a DUT 12. Current configuration of a scanner 20 and the components of other tester 10 are examined according to a system program and the identity of components to be configured is determined, along with the position thereof, by the scanner 20. Subsequently, the program retrieves a path connecting an instrument specified by a test program with a test point by studying the low level description of each scanner element. The test program then executes modification of the scanner state through a scanner driver 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic test equipment,
In particular it relates to the determination of the scanner status of such devices.

[0002]

2. Description of the Related Art A typical automatic circuit tester generally uses an attachment "nail bed". It includes a number of spring-biased probes ("pawls") that contact a number of test points on a device under test (DUT), which is typically a circuit board. These claws are in turn connected to "system pins" which lead to the terminals of the instrument which drive or detect the signal at said test point.

Complete testing of a particular circuit board would require a connection between the test instrument and multiple test points on the board, but any given portion of the test will typically test. Since only a few of the points are used, the number of test instruments can be much smaller than the number of possible substrate test points. Therefore, test instruments may be multiplexed. In automatic circuit testers, this multiplexing and associated switching device that connects between the instrument and the system is called the scanner.

Generally, the scanner is embodied in a plurality of circuit boards, each of which is inserted into the fixture along its edges. Some scanner boards additionally include an instrument that allows the scanner's switches to be connected to system pins, while other arrangements use individual cards for the instrument.
The former method is made by a manufacturer of testers and tends to "lock the purchaser" in the usage of the instrument,
The latter approach is often preferred. In response, the automated test equipment industry has responded by moving towards a "open construction" in which different test equipment manufacturers implement common instrument control conventions. They supply sockets that can be used with instruments manufactured by other suppliers, as long as the instruments follow common conventions.

To test a circuit board, the circuit tester follows a test program that includes a table of test instructions. Each instruction specifies a set of signals ("vectors") that are expected to be applied and / or detected at multiple test points during one clock cycle. In accordance with the test program, the tester applies a set of orders (sometimes called a "burst") specified by a set of instructions to the scanner in a condition, which results in a set of sets between the instrument and the test point. You can connect. The tester then generally changes the state of the scanner, thereby making a different set of connections before applying further signal sequence. The test program further includes a connection specification that reveals the intended set of connections.

At some point in the test program generation, the program is written at the stage of identifying each vector component and the type of instrument to which each test point to which these vector components are to be applied. That is, the program identifies the final connection between the instrument terminals and the DUT test point, without thereby identifying the scanner connection to which those connections should be made. The program at this stage is then specific for the particular tester configuration to translate the high level connection specifications into connection specifications that specify the scanner states required to make those final connections. Must be compiled by software written in.

[0007]

However, the configuration-specific nature of this conversion operation adds a significant burden. In particular, the compiler must be rewritten or greatly expanded for each new tester configuration. Some of the advantages of an open system, namely increased reconfigurability, are thus compromised.

[0008]

A scanner driver capable of operating a scanner in response to a test program capable of identifying a connection of an instrument to a test point at a stage where a scanner is not identified and operating a configuration of a scanner system which is rich in variety. We have recognized that a tester could eliminate the added burden and thus more easily obtain the benefits of reconfigurability. Of course, this type of scanner would need access to a library of information about the various possible scanner system configurations that it could encounter and consequently put the scanner system in the proper state. This kind of library can occupy too much memory to be practical. However, we further acknowledge that the required memory size can be kept manageable if the library is provided in a particular format.

In particular, rather than tabulating each possible configuration and the connections made in that state for each configuration, information at a lower stage, ie possible scanner components (eg scanner board). We have prepared, for each part, the switches it contains and the connection points to which it connects. Storage at this stage requires a smaller dimension of memory.

When a scanner driver operates with a given scanner system configuration, it is aware of the scanner system, for example, with respect to its components, the scanner board and their locations. So, in response to the connection details of the instrument to the test points of the test program,
The scanner driver retrieves via the scanner component to provide the desired connection thus identified.

By providing scanner-system configuration information as a scanner-specific low-level component information and the ability to retrieve from the scanner and the scanner-independent scanner configuration to drive the final scanner system configuration. We have obtained a scanner and independent driver that can take full advantage of the reconfigurability offered by the open system.

[0012]

DETAILED DESCRIPTION FIG. 1 illustrates in block diagram form one of many types of automatic circuit testers in which the teachings of the present invention may be used. The tester 10 is a driver / driver that supplies signals to the DUT.
DUT using a digital test instrument in the form of detector 14
Test 12 and observe the resulting signal produced by the DUT. In addition to the digital instrument 14, analog instruments such as the waveform generator 16 and the digital voltmeter 18 may be used as the tester.

To connect the test instrument to the DUT 12,
A typical automatic tester is a scanner 20 and a fixture 22.
To use. The scanner 20 provides a number of fixed position system pins 24 to the DUT and to the DU.
Carry the signal from T. However, these pins are not at the physical locations where the test points on any particular circuit board are aligned, but the signals on system pins 24 will have different physical locations for each board type or group. Must be directed. This is the purpose of the fixture 22, which provides a connection between a system pin 24 and a fixed pin (“pawl”) at a specified location on the DUT 12 with respect to the desired test point. Eggplant

For many DUTs, the number of pawls 26 is very large, but only a few of them are used at any given time. For example, a DUT may have many parts, which in total may require many test points, but at any given time the test program may have one independent part on the DUT or It is possible to test only the circuit. Therefore, this test involves only those test points that are in electrical communication with the particular terminal of the component or circuit and other 2.3 components or circuits whose operation is affected to disconnect the component or circuit. It doesn't matter. In testing that particular component or circuit, the tester leaves all other test points idle. Later, when the system tests another component or circuit on the board, it uses a subset of the other test points.

Since only a small subset of all the claws 26 is required for each part of the test, generally only a small subset of system pins 24 are used at any part of the test. Therefore, it would often be wasteful to provide each system pin 24 with its own independent test meter. This is especially true in analog instruments such as digital voltmeter 18 and waveform generator 16 because the number of such instruments used at one time is usually much smaller than the number of drivers / detectors 14. The tester is therefore
Includes a scanner 20, which is a matrix of switches and other circuit elements that switch the connection between the instrument and system pins 24 between bursts, such that the individual instrument is different for different parts of the test. Nail can be used.

The control circuit elements of the tester are the computer 2
8, its memory 29, sequencer 30 and scanner driver 34 may be embodied. To prepare the tester for a burst, the computer 28 communicates with the scanner driver 34, for example by industry standard MXI and VXI buses 36 and 38, so that the scanner 20 can connect between the instrument and system pins 24. Identify the connection so you can. The scanner driver 34 responds by applying a scanner control signal to the scanner over a separate scanner bus described below. It also functions as a VXI bus instrument bus and carries the instrument control signals that the computer 28 loads into the pin memory 32 with values representative of the signals that the individual test points should receive or expect to occur during the burst period. To do. Computer 28 may also program an analog instrument, such as digital voltmeter 18, if such instrument is included as a standard part of the tester. Instead, the scanner 20 is equipped with an analog instrument such as a waveform generator 16 that would not be present as a normal part of the system and would not be connected to the VXI bus.
Can be programmed independently by computer 28 if possible.

For real-time control during the actual burst, the computer 28 transfers control to the high speed sequencer 30, which clocks the driver / detector 14 and the pin memory 32, as well as other instruments. You can also control.

When the burst ends, the computer 2
8 is a pin memory 32 and, for example, a digital voltmeter 18
Read the results from, then change the state of the detector for the burst. Computer 28 also displays the results, either at that time or after another burst, using a suitable device, such as indicator 40.

FIG. 2 shows a physical arrangement in which certain elements of FIG. 1 may be assumed in an embodiment of the invention. FIG. 2 illustrates that the VXI bus 38 is conventionally provided as a back bus in a horizontal plane near the bottom of the tester chassis 42. The driver / detector 14 and digital voltmeter 18 of FIG. 1 receive meter control signals provided by a number of circuit boards inserted in the VXI backplane 38 to program and otherwise control their operation. Figure 2
Although only one of these substrates 44 is depicted, a typical tester will use many such substrates physically arranged in parallel. In FIG. 2, the connectors into which these other boards are inserted are omitted.

The circuit tester provides the scanner 20 on a plurality of circuit boards. Two scanner boards 46 and 47
Only one is shown in FIG. 2, but a large number will be used in a typical arrangement. In the illustrated embodiment, the scanner 20 of FIG.
Further includes a scanner back bus 50,
Is separate from the VXI instrument bus 38, but physically parallel to it. The scanner board 46 is the board 44.
At the upper edge of the connector 48, the board 44 provides a port for an analog instrument or driver / detector to drive and / or detect signals. Also the scanner board 4
6 and 47 are plugged into a connector such as connector 51 on scanner bus 50 from which it receives scanner control signals. In addition, they are connected to the instrument and DU by the bus 50.
Send and receive T signals.

For simplicity, FIG. 2 illustrates a conventional VXI backplane 38 with which the computer 28 communicates with the scanner 20.
Most of the MXI bus connections have been omitted. However, as explained above, the computer sends the signal to VXI.
Some of these signals transmitted to the back surface 38 and properly decoded are forwarded by the scanner driver 34 to the scanner 20, which in FIG. 2 is oriented with the circuit board 34 parallel to the scanner boards 46 and 47. It is shown as being embodied in. "Slot 0" board 5
2 connects the VXI rear surface 38 and the scanner driver 34.

The upper edges of the scanner boards 46 and 47 provide connectors 54 and 56 which are
It includes some of the system pins 24 of FIG. 1 with corresponding connectors on other scanner boards not shown. There is also a connector 58 included on the upper edges of the scanner boards 46 and 47 for attaching the coaxial cable from the external waveform generator 16 of FIG. 1, for example. (Of course, the waveform generator
It can be provided as if a driver / detector or voltmeter was provided. That is, it can be connected between the scanner board and the VXI bus. 3.) To test the DUT 12, the tester 10 follows a test program 60 written for the DUT, some of its contents residing in the memory 29 shown in FIG. However, according to the present invention, the test program 60 is not specific to the particular tester configuration employed by the test system 10. In particular, it is not based on any assumptions regarding the position of the various types of instruments and scanner boards 44 and 46 within the tester. Therefore, in specifying the arrangement of connections for a particular burst, it does not explicitly give the scanner status. Instead, it says, for example, that the first driver / detector should be connected to the first test point, while the output terminal of the digital voltmeter should be connected to the second test point. Identify. The tester then translates from this stage of the description to the stage of description specific to the particular arrangement of tester 10.

To this end, the system prioritizes the execution of the test program 60 by the running system program 62 which includes the initialization of the routine that determines the current tester placement. For example, assume that boards 44 and 46 have the (very simplified) topology shown in FIG. 4 and are in the 22nd tester slot. Further assume that fixture 64 is installed and its connection is as shown in FIG. From either a command from the user or a query of the fixture's identification register (not shown), the system program is informed about the identity of the fixture and includes a description of the various fixtures that the tester will use. The description of the fixture is obtained from the fixture description file 65. Such files typically reside in the mass storage memory of tester memory 29. The attachment description is DUT
The user's naming for the test points of the scanner board and the scanner board terminals ("system pins") to which the fixture will connect those terminals to the expected scanner board when it is in the expected position for testing the board. Clarify the correspondence of.
For the three test points shown in FIG. 4, the items shown in Table 1 may be used.

Table 1. Attachment description file TP1 V22. A TP2 V22. B TP3 V22. C The first item in the left column identifies the test point that the user calls TP1, and the first item in the right column is that the fixture points test point TP1 to the 22nd slot ("V22"). Scanner board, especially the D that the fixture is aimed at in its slot
It is indicated that a connection is made to a connection point called connection point A of the type of board required for testing the UT. The fixture likewise connects the test points TP2 and TP3 to the connection point V22. B and V2
2. Connect to C.

Next, the system program proceeds to the process of determining the scanner configuration. In particular, the signals transmitted on the scanner bus 50 allow the system program to obtain the type identification content of the internal type register from the control circuitry 74 on the scanner board 46. As mentioned above, the fixture information of the illustrated embodiment provides proper identification and placement of the scanner board of the tester, in which embodiment this step merely verifies that a suitable scanner board is present. Is. In other embodiments, test point connections may correspond thereto, but such information generally identifies test point connections only by physical edge connector locations that would not include a particular scanner configuration. You can do it.

Using the identification information thus obtained, the system program 62 makes a description of the specific scanner board type identified by the control circuit element 74 of the board 46 from the scanner description file 66 which is an element library of scanner board description. obtain.

The contents of this file may be of the type identified in Table 2.

[0028] The names HF1 / I and HF1 / O distinguish their attachment points from others for the purposes of explanation.

Each item of the relay bit string in this table represents a different bit position in the relay status register 76 of the scanner board 46. Each bit position represents the state of a different bit position of the relay 78 that makes up the scanner board 46. The "Side 1" column shows the name of the connection point on one side of the relay, and the side 2 column contains the name of the connection point on the other side of the relay. Therefore, by sending a control signal on the scanner bus 50 that sets the contents of bit position 01 of the relay status register 76, the computer can thereby close the relay connecting the connection point A to the connection point E. Similarly,
The connection point E is in turn connected to the connection point G by closing the relay whose state is represented by bit position 10. Further, Table 2 identifies certain connection points as terminals on the scanner board. In particular, Table 2 thus describes connection points A, B and C (which are the connector terminals on the side edges of the fixture) and connection points G, H and I (which are the connector terminals on the side edges of the instrument). is there.

It is this type of storage of scanner configuration information that allows the use of scanner drivers independent of the scanner. Any such driver, of course, must be informed of the current scanner system configuration and must reference some general library of scanner configuration information for details of the current information.
However, such a library, if provided, would be prohibitively large, resulting in a final combination of connections, eg, in the form of full scanner system state. On the other hand, in the form shown in the figure, only the closure of individual relays and the resulting connection of each individual set of connection points is filled in, and the necessary scanner details can be stored in a reasonable amount of memory. Yes, the desired final connection can be retrieved by the driver's scanner independent search routine.

In summary, we have a library of (1) a manageable size of scanner board specific intermediate junction level information and (2) a final library such that individual parts of the library are required. By separating the final connection information source from the scanner-independent search program that converts to the connection level, the scanner-independent driver can be executed.

The initialization program then queries the instrument slot on VXI bus 38. When a query specifying the 22nd slot appears on the VXI bus 38, the output from the board type identification register of the control circuitry 68 of the board 44 is applied to the bus 38 and the system program 62 uses this board type information. Fetch information about board 44 from instrument interface file 67. File 67, for each variation of the instrument as used in the tester, contains a description of that instrument's interface to each type of scanner board to which it can connect. Therefore,
The initialization program captures information that describes the interface between the instrument type on board 44 and the scanner board type on board 46.

For example, the board 44 is of a type named DSVM, and this kind of board has two drivers (indefinite type).
Assume that detectors 14a and 14b and digital voltmeter 18 are included. Instrument interface file 6
The left column of Table 3 displaying the appropriate portion of 7 is the two conductors of the instrument commonly known to the user as D / S1 and D / S2 (ie driver / detector input / output conductors). It carries a conductor known as the DVM (ie, the input terminal of the digital voltmeter 18).

Table 3. Instrument Interface Description File D / S1 G DVM H D / S2 I For each of these conductors, the instrument interface file contains a separate corresponding entry for each type of scanner board into which the instrument board can be inserted. Each item specifies the name of the terminal on the scanner board to which the conductor described by inserting the instrument board into the scanner board corresponding to that item is connected. The right column of Table 3 lists the items corresponding to the type of scanner board that the system program identified when it occupied the slot into which the board of the instrument was inserted.

From this information and the identification of the slot in which the system board is located, the system program can identify the scanner terminal name and instrument that distinguishes the terminals on the scanner board from each other as well as from similar scanner terminals on other scanner boards. The items of Table 4 that clarify the correspondence with the conductor names are placed in the terminal decode table 70.

Table 4. Decode table item Slot Instrument lead wire Scanner terminal 22 DSVM D / S1 V22. G 22 DSVM DVM V22. H 22 DSVM D / S2 V22. I Table 4 shows that the system program recorded the presence of a DSVM type instrument installed in the scanner board at slot 22 and that the instrument terminals designated D / S1, DVM and D / S2 are V22. G, V22. H and V2
2. It is shown that they are connected to the scanner terminal of I, that is, the connection points G, H, and I of the scanner board of the 22nd slot.

From the information in Tables 2 and 4, the system program then creates a scanner connection point connection table 77 that lists for each individual connection point the other connection point to which the relay can connect it. Table 5 depicts the items for the connection point quoted as connection point A in the individual board data.

Table 5. Scanner connection point connection table Item Connection point Is it a connection point for the usage counting terminal? Connection item Relay V22. A 0 Yes V22. D 2201 V22. E 2202 V22. F 2203 Now connection point V22. This attachment point, known as A, feeds into a usage count whose content is initially 0, but can change during the execution of the test. Connection point V22. For A, there is a table of "connection items", that is, the connection points to which it can be connected and the associated relays by which those connections are made. The system program compiles this table from the information in the side 1 and side 2 parts of the scanner description file.

Also included in the connection point item is an indication of whether the connection point is a "terminal connection point" and, if so, what type of terminal connection point it is. .. Terminal connection points are those that connect directly to the instrument or fixture or scanner bus. The purpose of such a display will be clear from the description of the connection algorithm.

In addition to the items in the connection table that are easily apparent from the scanner description file information, the system program adds information about the connection of the internal board. See, for example, Sullivan et al., Filed February 22, 1991, “Automatic Circuit Tester with Separate Instrument and Scanner Bus (Aut), incorporated herein by reference.
Omatic Circuit Tester wit
h SeparateInstrument and and
The scanner bus 50, which conducts control signals to the scanner, may also conduct test signals between the scanner boards, as described in U.S. Patent Application No. 660,289 entitled "Sczner Busses". Therefore, the final pass of the set part of the system program adds information about the connections between the scanner boards. The specific names HF1 / I and HF1 / O in Table 2 here have the following meanings. That is, they indicate that their connection point is connected to one or the other side of a particular signal line of the scanner bus. As a result of this display, the system program is, for example, V22. The connection table for HF1 / I has V21. HF1 / O was added, and V22. HF1 / O
Connection table for V23. Add HF1 / I.

The manner in which tester 10 uses this table will now be described in connection with a simple test example. After the initialization described above, the test that the computer 28 is going to perform is
For the sake of example, we include a burst that we assume is applied to two cooperating connections. In the first connection,
The test points TP1 and TP2 and the user sets DSVM1. D
/ S1 and DSVM1. The terminals of the instrument, referred to as DVM1, are all connected together. In the second connection, the test point TP3 is connected to the instrument terminals DSVM1. It is connected to D / S2.

FIGS. 5 and 6 depict an exemplary routine that a tester system program 62 employing the present invention may use to determine how to make these connections. The first block 90 in FIG. 5 represents reading the first connection from the test program 60. The test program has names that are unrelated to their scanner shape,
That is, TP1, TP2, DSVM1. D / S1 and D
SVM1. These terminals are identified by DVM1. In this respect, the table still does not include the instrument name "DSVM1" as specified by the test program, but at least DS
It has what is called a VM, and "DSVM1" is "DSV
The first of M ”. Therefore, the system program searches its decode table for the DSVM entry of the instrument row and finds that of slot 22. (Users usually prefer this automatic instrument naming ability, but they are free to give the user the choice of choosing on their own.)
As shown in Table 6 in the instrument position table 88 (Fig. 3) D
By entering an item that identifies the location of a particular DSVM that can be considered SVM1
Is designated as "DSVM1".

Table 6. Instrument position table item Instrument name Slot number DSVM1 22 Next, the routine checks the instrument position table 88 and the terminal decode table 70 (FIG. 3) there, and sets the instrument terminal name of the test program 60 to the scanner terminal name to which they are connected, That is, the terminal V22. A, V22. B, V22, G and V22.
Proceed to the block 92 step of converting to H. The routine optionally has one of these terminals, for example terminal V22. A
Is selected as the "basic" terminal, and the execution table 96 (Fig. 3) is selected.
, And the other three terminals are placed in the search table 98. Then the task is to find the path from the base terminal to the lookup table terminal.

The block 100 indicates the next connection point V22. Denote A (in this case the only attachment point in the run table) as the test attachment point it handles. The processing of the test attachment point determines whether any single relay connection from the test attachment point to another attachment point is likely to be part of the path from the base attachment point to the lookup table attachment point. including.
For this purpose, the system program 62 checks the item of the test connection point of the terminal decode table 70, and for each “connection item” of the item of the terminal decode table of the test connection point, the connection item is (1) the search table. It determines whether it is one of the connection points, and thus is certainly part of one of the desired connection paths, or (2) meets the criteria for disqualification and can be reliably excluded as part of the path. If the answer to both questions is no, then the connection item must be placed in the run table for further processing. This is the function of the steps repeated by blocks 101-106.

In particular, in the first pass through the routine, the routine may not be checking the connection items at all test attachment points. Therefore, the result of the block 101 step would be positive. As Table 5 shows, test connection point V22. A (FIG. 4), one of the connection items is the connection connection point V22. D (FIG. 4), block 102 represents this as the first connection item to be checked. The decision block 103 represents the determination of whether this connection point is one of the connection points in the run table, ie whether it has already been identified as a potential bond of the desired connection path. .. If so, no further processing will be necessary, so the loop will start for the next connection item. If not, the routine proceeds to the test of block 104 which determines if the current connection item is in the lookup table. Connection item V22. D is three terminals V on the search table
22. B, V22. G and V22. The result of this decision is negative, as it is not one of the H's.

This means, however, that connection point V22. D is
It does not mean that it cannot be part of the path that ultimately leads to one of the terminals to be connected. Therefore, the routine is to determine that the connection between the test attachment point and the connection item currently under consideration is
Proceed to the next step of determining whether the base terminal can be removed at this point as a potential part of the path for one of the terminals to be connected. Block 105 examines, for example, an item in the scanner connection table of the current connection item (as opposed to the item in the test connection point) and determines if that item is used, ie its usage count field. Represents determining if an item has a value other than 0. If so, this connection item cannot be used as part of the current connection. This is because doing so would give the terminal of the current connection less than the terminals connected by the connection whose connection item is already part.

Current connection item V22. If D is used, the routine proceeds to decision block 106. The step represented by this block branches on the contents of the terminal connection field field of the scanner connection connection table of the current connection item. If the connection item is a terminal connection point, ie it is a fixture or instrument terminal, it should not be tied to the current connection. Instead, it should be reserved for some other connection, the purpose of which is to connect that terminal to another. If the tests in blocks 104 and 106 cannot exclude the current connection as a binding of the desired connection path, then the connection item is an execution table, that is, the connection item may be included in the connection. Added to the table of attachment points that should be examined as being. When any attachment point other than the base attachment point is placed in the run table 96, it indicates the connection point in its scanner attachment point connection table entry as well as an indication of the relays that make the connection between those attachment points. It should be accompanied by a backward pointer consisting of the name of the underlying attachment point found in step 102. Then the routine
If any of the steps represented by blocks 103, 105 and 106 make a positive decision, then return to decision block 101.

Connection Connection point V22. When D is taken into account, there are two more connection items, namely connection point V22. E
And V22. F is the current test connection point V22. A remains in the Scanner Junction Connection Table entry for A, and the routine is responsible for those two connection points because it is V22. Proceed through the same sequence of steps as did for D. However, if the connection point V22. When done for F, the result of the decision represented by block 101 is negative and the routine returns to the determination of whether there are any items left in the execution table represented by block 99. The routine will block 9 if it has already found a route connecting all of the terminals the test has named for this connection.
It does not reach step 9. Therefore, if no line remains in the execution table, no connection path can be found due to the criteria imposed by the routine of FIG. The routine proceeds to an alternative routine that either reports this fact to the user or does not impose the criteria of block 106.

However, this is usually prevented by the number of test designs and tester tools, and the result of block 99 is positive. The result is step 100, where the next item in the run table is selected as the test connection point. For example, the next item is the connection point V22. It is D.

Inspecting the scanner connection point connection table entry for the new connection point, the routine makes a positive decision at step 101 and at step 102 the connection point V22. A, the previous test attachment point, is selected for processing. This connection point is already in the execution table (and in fact "executed") and the resulting positive result of the test of block 103 is thus again to allow the test to take into account the coupling between these two connection points. It is possible to avoid it.

Next, the routine obtains another positive result from step 101, the test connection point V22. Connection point V22.D, which is the next connection point of the scanner connection point connection table item. Perform steps 102 and 203 for B. Since the connection point is not in the execution table, the routine executes the connection point V22. B
Goes to step 104 which determines that is completely in the lookup table. That is, a path was found from the base connection point to one of the lines to which it was connected. Therefore, the routine
Proceed to the step represented by block 108. In this step, the current connection item V22. B is placed in the discovery table 118 and removed from the lookup table.

Next, the routine proceeds to a decision step, represented by block 109, which indicates that more terminals remain in the lookup table. That is, the connection point V22. G and V22. The route to H has not yet been found. Next, in a connection table in a certain connection form, the connection point V22. It is also possible that a connection point such as B can be used as a connection of paths from the base connection point to the other connection points in the second table.
Therefore, if the search table is not empty, the current connection item, connection point V22. The process of B continues even if it is known that the attachment point is now terminating with the desired connection path remaining. However, the connection point V22. Since B is a terminal connection point, branching at step 106 prevents it from being added to the run table.

The steps represented by blocks 101 and 102 are again performed and the routine proceeds to block 10
3 instruct, the test connection point V22. Connection point V22.D next to the scanner connection point connection table item of D. Determine if G is already in the run table. Since it is negative, the routine determines whether the current connection item is in the lookup table block 1
Perform 04 tests. The positive result of this test is that connection point V22. Remove G from the lookup table and place it in the discovery table.

The next iteration is likewise for the terminals V22. Find out that H is in the lookup table. The terminal V22. H is therefore removed from the lookup table and placed in the discovery table. Connection point V22. Test 109 gives a positive result because H was the last entry in the lookup table. That is, the path is an arbitrarily designated "basic" terminal V22. A (also test point TP
(Known as 1) through the scanner circuitry to a first connection to all the terminals to which it had to be coupled.

All that remains is to set the relays in their path. This step, represented by block 110, starts with one of the entries in the discovery table and follows the associated pointer to the execution table, which represents the previous attachment point of the identified path. It then follows the pointers associated with that attachment point and continues in this way until it reaches the underlying attachment point. When it does, it compiles the entry into connection table 124 (FIG. 3) as the first connection by placing the join it encounters according to the pointer in that entry.

Discovery table connection point V22. By starting for example, the routine causes the connection table entry for the first connection to point V22.B. B to connection point V22. Connection to V and connection point V22. D to connection point V22. Put the bonds up to A. Next discovery table connection point V22. Starting for that connection point, the routine proceeds from that connection point to connection point V22.G. D
Only joins to F. The connection point V22. D to basic connection point V22. This is because further connections up to A are already listed in the connection table item of the first connection.

The routine executes the last discovery table item line V22.
Complete the item by tracing back from H. Table 7 shows
Gives the resulting item.

Table 7. Connection table item, Connection 1 Connection 1D: 1 First connection point Second connection point Relay bit V22. B V22. D 2203 V22. D V22. A 2200 V22. G V22. D 2209 V22. HV22. D 2212 With the compiled path information for the first connection, the routine then activates the relay by setting the relay bits listed from Table 7. It also increments the usage count entry in the scanner connection point connection table for each connection point placed on that connection. (The usage count field is incremented only once for each splice point, even if that splice point is listed more than once in the route information for the first connection.) The routine of FIG. Block 1
Exit by emptying the temporary search, find, and execute tables, as indicated by 11.

As mentioned above, a second connection must be made for this burst. Regarding the connection request for this connection, the test point TP3 is the driver / detector terminal D.
SVM1. It is connected to the D / S. References to instrument market and terminal decode tables 70 and 88 refer to this as scanner terminal V22. C to scanner terminal V22. Move to I.
Next, the system program is processed in the manner described above with reference to FIGS.
Follow the routine. The result is an item of the second connection (given in Table 8) to the connection table which increments the usage count field and sets the displayed relay.

Table 8. Connection table item, connection 2 Connection ID: 2 First connection point Second connection point Relay bit V22. C V22. E 2207 V22. EV22. I 2216 With a relay register, such as register 76 set in scanner driver 34 according to the routine described above, relay 98 assumes that they are in the proper connection,
The computer 28 prepares for an upcoming burst by loading the memories 32a and 32b with the values to be applied during the burst. Computer 28 loads other pin memory devices as well. Upon entering these values, the detector 30 is then enabled to operate the various instruments to apply the burst and record the results.
In FIG. 4, memories 32a and 32b represent memories that apply vector elements and record the results, and computer 28 typically results in the continued DVM results in other memories 120 before applying the next burst. Not only these results are read out.

Also, before applying the next burst, it configures the scanner 20 to make the appropriate connections for the new burst. The test program 60 causes the next burst to be decoupled from the test points TP1 and TP3 without using the second driver / detector connected to the test points TP1 and TP3, and the first driver / detector
Suppose the test program 60 indicates that it should be applied using the detector. One way to make all of these connections is to reset all relays and then execute the routine of Figure 5 for this connection. That is, the scanner can be reset and started from the beginning, as was done in the conventional manner. However, in some cases, such a method may require significantly more relay operation than the consequences of placing it on a common connection for previous and upcoming bursts. Therefore, we assume that the system program changes the scanner state "incrementally" rather than by resetting all scanner relays after each burst.

This incremental method is most effective when the technique of the present invention is used. Because the test branches with different burst results, for a given burst, the difference between that connection and the connection of the previous burst will change from one use of the test to the next. Thus, for a given connection, the set of couplings that minimizes relay switching for one test run is different from the set that minimizes relay switching for another test run. However, the traditional way in which a test identifies a connection for a particular relay state is
It is not suitable to allow such a difference. The invention, in which the test program specifies the connection with respect to the final terminal to be connected, rather than with respect to the particular path over which the connection is made, is readily implemented in systems where the set of couplings is determined between bursts, The present invention readily tolerates such differences, as prior relay states can be taken into account in determining the route, as shown in block 105 of FIG.

Therefore, according to the incremental method, the system program compares the new set of connections with the previous set of connections, the first connection (ID = 1) has to be canceled and the instrument line DSVM1. It is concluded that a third connection must be made connecting D / S2 to test point TP1.
Thus, this method resets the bit in the relay register recorded on the first connection, thereby removing the connection and reducing the usage count of the connection points it contains. That is, the connection point V22. A, V22. B, V2
2. D, V22. G and V22. Decrease usage count for H. The routine of FIG. 5 is then executed to find a suitable binding to implement this third state. Table 9 gives this result.

Table 9. Connection table item, connection 3 Connection ID = 3 First connection point Second connection point Relay bit V22. A V22. D 2201 V22. D V22. The next burst is applied using this third connection in place at I 2215. The scanner state then changes and vector bursts occur in this manner until the test is complete.

[0065]

A review of the above description reveals that the tests can be made virtually hardware independent when the method of the present invention is used. As mentioned above, the test program 60 specifies connections in terms of test terminals and test points and does not require any changes when either the instrument or scanner configuration changes. The present invention thus constitutes an important advance in the art.

[Brief description of drawings]

FIG. 1 is a block diagram of an automatic circuit tester of the type in which the present invention can be used.

FIG. 2 is a partially cutaway perspective view of a tester of this type.

FIG. 3 is a diagram selectively showing the contents of the memory of the tester.

FIG. 4 is a block diagram of an exemplary scanner and instrument card that can be used by the tester.

FIG. 5 is a portion of a flow chart of a routine of the type that can be used by a tester employing the present invention to determine a scanner state for a tester signal burst.

FIG. 6 is the remaining portion of a flow chart of a routine of the type by which a tester employing the present invention may be used to determine scanner status for tester signal bursts.

[Explanation of symbols]

 10 Tester 12 DUT 16 Waveform Generator 18 Digital Voltmeter 20 Scanner 22 Fixture 28 Computer 29 Memory 30 Sequencer 32 Pin Memory 34 Scanner Driver 44 Board 46 Scanner Board 60 Test Program 62 System Program 65 Fixture Description File 66 Scanner Description File 67 Instrument interface file 68,74 Control circuit element 70 Terminal decode table 77 Scanner connection point connection table 88 Instrument position table 96 Execution table 98 Search table 118 Discovery table 124 Connection table

Claims (2)

[Claims] 1. A DU adapted to mount a different type of replaceable instrument having an instrument terminal therein and a DU.
Automatic, adapted to mount therein a fixture including a different type of replaceable DUT having mounting terminals that provide connection to a test point of T, and further adapted to mount a scanner element of a different type therein. A circuit tester in which the scanner element connects a scanner connection point and a pair of scanner connection points, some scanner connection points connected to instrument terminals and other scanner connections connected to fixture terminals A scanner switch operable to form a scanner having a point, between a command to identify a signal burst and an indicated meter terminal and an indicated DUT test point during the associated signal burst. Adapted to receive a test program containing relevant connection details identifying the connection and in response to the identified burst In an automatic circuit tester for operating an instrument mounted in: A) including an element library of scanner element descriptions, each scanner element description including a table of scanner switches, and for each scanner switch said scanner connection point B) the identity of the scanner elements currently in the tester, the scanner switch table, the instrument terminals for each switch and the DUT.
A configuration compiler adapted to receive an identification signal representative of a DUT test point connection and an instrument terminal generating a scanner description consisting of a test point and a scanner connection point to which the switch connects; C) coupled by a scanner switch, It is searched by a scanner description for a sequence of scanner connection points that can form a path from a specified instrument terminal to a specified DUT test point, thereby activating the scanner switch to complete the path found. An automatic circuit tester, comprising: a scanner driver that responds to connection details for responding. 2. A) the scanner element includes an identification circuit adapted to receive an interrogation signal and responsively generate an identification signal representative of the identity of each element; and B) the constituent compiler interrogates. The automatic circuit tester of claim 1 including means for applying a signal to said scanner element, said identification signal received by said configuration compiler being a signal generated by an identification circuit.