Design of a signal-oriented automatic test system resource allocation method

ATS (Automatic Test System) can automatically test and diagnose faults on the equipment under test. The TPS (Test Program Set) developed in the traditional instrument-oriented ATS involves direct access to test resources. When TPS is ported between different platforms or the test instrument resources are changed, the test program needs to be modified a lot, and the portability and reusability are poor.

ATML (Automated Test Markup Language) uses a signal-oriented structure to standardize the description of ATS.

ATML describes the test requirements as the measurement/stimulus signal requirements of the UUT port, and the test resource capabilities as the signal capabilities of the instrument resource ports, and implements the allocation of instrument resources through signal matching. During the test execution, the test program calls the signal-oriented instrument driver to implement the test operation based on the results of the instrument resource allocation. The TPS developed based on ATML does not contain any operations for hardware resources. When the TPS is ported between different platforms, the resource allocation module can re-allocate test instruments to the UUT port, which improves the portability of the TPS.

1. Instrument Capability Description

The ATML ATS relationship diagram is shown in Figure 1.

In ATS, the main function of the instrument is to generate or measure the required signal of the UUT port. Traditional test instruments are often special instruments with a single function. There are many instruments in ATS. With the increase of the devices under test, there are more and more special test adapters, which leads to the increasing scale of general ATS. In recent years, software-controlled and functional combination synthetic instrument technology has emerged, such as Ai7 technology, which realizes the functions of 7 instruments by a synthetic instrument module. Each channel of the reconfigurable instrument resources independently developed by our unit can be software-defined as common test instrument resources such as AD/DA/counter/DMM, eliminating the resource allocation link (signal switch matrix); at the same time, the reconfigurable instrument has an ultra-wide range and can be used for signal conditioning without the use of an interface adapter.

In order to achieve flexible reloading of TPS for signal development and independence of instruments, ATML does not directly use the physical ports of instruments, but defines signal capabilities and logical resources in the instrument description document, and allocates different signal capabilities to instrument ports through mapping capabilities to resources and connecting resources to ports. The capacity of the entire test system is the sum of the capabilities of all instruments in the test workstation.

Taking the multimeter resource in the reconfigurable instrument as an example, the mapping relationship between its capabilities, resources, and ports is shown in Figure 2.

(1) Define the signal capability of the instrument

The signal capability of an instrument defines the type of signal that the instrument can generate or measure. The signal capability of an instrument is described using the BSC (Basic Signal Component) library and the TSF (Test Signal Framework) library of STD. You can also use a combination of basic signals in the BSC library and the TSF library to customize the complex signals required for testing. Taking the DC voltage measurement capability as an example, the amplitude range is -400~400 V, and the accuracy is 0.1%. Its ATML description is as follows:

(2) Define logical resources

Logical resources define the functional modules inside the instrument and are used to connect the instrument's signal capabilities to the physical ports. The multimeter resources shown in Figure 2 contain four logical ports: P1, P2, P3, and P4.

(3) Define the physical port of the instrument

The physical port defines the external port of the instrument, the port in Figure 2:

HI, LO, Sense_HI, Sense_LO.

(4) Mapping signal capabilities to resources

The CapabilityMap element is used in the instrument description document to describe the mapping relationship between signal capabilities and logical resources. Its structure is: Capability-Map/Mapping/Map/Node/Path. By adding Mapping elements, multiple signals are mapped to the same resource, which can describe that a resource can generate/measure multiple signals, but can only generate/measure one of them at the same time; by adding Mapping elements, a signal is mapped to multiple resources, which can describe that a signal can be generated/measured by multiple resources; by mapping multiple signals to a resource in the same Mapping element, it can be described that a resource can generate/measure multiple signals at the same time; by mapping a signal to multiple resources in the same Mapping element, it can be described that a signal occupies multiple resources; by adding multiple Map elements in the same Map-ping element, it can be described that multiple ports between signals and resources are connected; by adding multiple Node elements in the same Map element, it can be described that one-to-many or many-to-one connections between signals and resources; the Path element is used to describe the location of the capability or resource port in the instrument description document. Through the above combination, the description of complex relationships such as mutual dependence or constraints between specific instrument functions can be completed.

(5) Connect resources to physical ports

The NetworkList element is used in the instrument description document to describe the connection relationship between logical resources and physical ports. Its structure is: NetworkList/Network/Node/Path. By adding the Network element, multiple logical connection lines between resources and ports are described; the Path element is used to describe the location of resource ports and physical ports in the instrument description document.

2 Test Requirements Description

ATML uses STD to describe the test requirements in the test description document. The stimulus signals or measurement signals required for all ports and test points of the UUT are described in the element TestDescription/DetailedTestInformation/Action/Behavior. The structure of the Behavior element is shown in Figure 3.

The Operations element and the IeeeStd1641 element contain references to the STD standard. Taking the Operations element as an example, the description method of test requirements in ATML is explained. The Operations element uses 17 predefined types of operations to describe the behavior of Behavior, among which the OperationSetup type of operation is used to create the required signal, and the OperationConnect type of operation is used to connect the signal to the port or test point of the UUT. Using the OperationConnect operation to connect the signal signal1 created in the OperationSet-up to a port of the UUT, the required signal of the UUT port can be described as the signal1 signal.

3. Design of Instrument Resource Allocation Module

The instrument resource allocation module realizes the mapping of instrument resource ports to UUT ports by matching the test requirements with the test resource capabilities. The design scheme of the instrument resource allocation module is described using UML (Unified Modeling Language), and its use case diagram is shown in Figure 4.

In the instrument resource allocation module, by loading the test description file, the test workstation description file and the instrument description file, the test requirement information and the test system capability information are obtained, and the allocation of instrument resources is realized through signal matching. By analyzing Figure 4 and abstracting the use case, the class diagram of the instrument resource allocation module is obtained as shown in Figure 5.

A brief introduction to the classes involved in the class diagram is as follows:

(1) Instrument resource management: Allocate instruments according to the signal requirements of each UUT port and the instrument capability list, generate instrument working mode configuration information, and obtain the connection relationship between the workstation and the UUT based on the connection relationship between the instrument and the test workstation, and finally generate the physical connection information from the UUT port to the workstation port.

(2) Instrument class: Load the instrument description ATML document and parse it to obtain the instrument capabilities, logical resources, instrument ports, and mapping information from capabilities to ports; generate the instrument working mode configuration file based on the instrument resource allocation results.

(3) Test description class: loads the test description ATML document and parses the document to obtain the UUT port, test point and required signal information.

(4) Test workstation class: load the test workstation description ATML document, parse the document to obtain the test workstation port, instrument resource information and the connection information between the instrument and the workstation.

(5) Physical connection category: Generate the physical connection file from the UUT port to the test workstation port based on the instrument resource allocation results.

By analyzing the static model of the instrument resource allocation module, a sequence diagram of the interaction of system objects over time is obtained as shown in Figure 6.

As shown in Figure 6, the process of instrument resource allocation is as follows: parse the test description file to obtain the demand signal of each port of the UUT; parse the test workstation description to obtain all the test instrument information in the workstation and the connection relationship between the instrument and the workstation; parse the instrument description file to obtain the instrument capability list and the connection information from the instrument capability to the instrument port; allocate instruments according to the signal requirements of each port of the UUT and the instrument capability list, generate a reconfigurable instrument working mode configuration file, and according to the connection relationship between the instrument and the workstation, obtain the connection relationship between the workstation and the UUT, and generate a physical connection file from the UUT port to the test workstation port.

The operation of allocating instrument resources is described in the form of an activity diagram, as shown in FIG7 .

The process of allocating instrument resources is as follows:

(1) Query the UUT port demand signal list and obtain the demand signal R_Signal of the UUT port UUT_Port; exit if the list is empty;

(2) Query the signal capability list to obtain the signal capability A that meets the required signal R_Sig-nal; if it fails, R_Signal is not matched successfully, and the current test configuration cannot meet the test requirements, go to (1);

(3) Query the CapabilityMap list and obtain the mapping that contains signal A; if it fails, go to (2);

(4) Obtaining the resource R that generates/measures the signal A by mapping;

(5) Check whether resource R is idle from the resource list. If resource R is already in use, go to (3); if resource R is idle, go to (6); if resource R is conditionally idle (i.e., resource R can generate/measure multiple signals at the same time, and resource R has been used to generate/measure one or more of the signals), go to (7);

(6) Query the instrument's NetworkList to obtain the instrument port INST_Port connected to the resource R; query the test workstation's NetworkList to obtain the workstation port Sta_Port connected to INST_Port, and generate a connection between Sta_Port and UUT_Port; the test instrument calls the signal-oriented instrument driver corresponding to the signal capability A, and the INST_Port port generates/measures the demand signal R_Signal of the UUT_Port port; go to (1) to continue matching the next item;

(7) Query the connection list between resource R and instrument ports, workstations, and UUTs, and obtain the UUT port R_UUT_Port to which resource R is connected; compare UUT ports UUT_Port and R_UUT_Port; if the two are the same, use the instrument connected to UUT_Port to generate/measure signal R_Signal, and go to (1) to continue matching the next item; if the two are different, go to (3).

When there are multiple instruments that meet the test requirements, the instruments should be sorted according to certain principles to determine the final test instrument. You can refer to the scheduling methods such as highest accuracy, balanced use of instruments, and instrument usage habits for testing.

4 Conclusion

This paper studies the signal-oriented description method of test system capabilities and test requirements in ATML, and gives specific description examples; the software structure of the instrument resource allocation module is designed in detail using UML. The instrument resource allocation module allocates instrument resources to the ports to be tested of the UUT by matching the signals of the test system capabilities and test requirements. The signal-oriented resource allocation method improves the portability of TPS in ATS, and the method proposed in this paper can provide guidance for other similar studies.