Multisite Digital Test System Design

Knowledge Base Article # Q200340

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Summary The following article discusses the relative merits of two types of multi-site digital semiconductor test system designs. This article focuses on using GtDio6x and ATEasy software packages to program and control PXI GX5960 series or the GX5296 digital IO boards.

Introduction

Semiconductor digital tests, especially digital test programs converted from simulation files such as STIL, WGL, VCD, EVCD or ATP, are often required to be expanded into multiple DUT test sites. This article discusses the system hardware and software requirements to perform multi-site testing using the GtDio6x product line and ATEasy®, to provide a cost effective solution.

Digital Design Considerations

When designing a multi-site test program the tradeoffs between cost and performance may not be completely understood. After evaluating the performance and capability of the GX5296 or the GX5964 series of dynamic digital instruments, it may be logical to assume that the large number of channels of a single GtDio6x board should be capable of providing a multi-site digital test solution. While this solution is possible, it cannot yield the performance of a system that uses a digital resource or board per DUT test site.

Domain Per Site Solution

Marvin Test Solutions recommends that multi-site test systems be designed such that each DUT test site uses its own digital domain, as shown in Figure 1. This solution provides the fastest multi-site test performance, as each DUT test site can be run independently.
 Multi-Domain Block Diagram
Figure 1 – Multi-Domain Solution Block Diagram

Using this configuration, all digital resources are available for each DUT test site. The test status of each DUT test site can be instantly identified by reading the Real Time Compare (RTC) error status register. In addition, the system can be designed such that each DUT test site will use the same digital test file and test program. DUT test sites can be can easily be expanded by adding additional digital domains. Using ATEasy® a multi-threaded test program can easily be created to perform this testing.

 Domain Per Site Solution
Table 1 – The relative merits of the Multi-Domain Solution


Single Domain Solution

A multi-site digital test system designed using a single digital domain as shown in Figure 2 has several disadvantages. First, each test site can no longer use the same digital file. This solution will require a separate application to create the additional test sites from the original digital file. This additional application would need to copy the original channel and vector data to all of the new DUT test sites.
 Single Domain Block Diagram
Figure 2 – Single Domain Solution Block Diagram

This also requires a much more complicated test program to determine DUT test site status. As with the multi-board solution if the RTC error status register is zero then all DUT test sites pass. But when a failure occurs, the status of each DUT test site cannot be determined by simply reading the RTC error status register. The DUT test status must be determined by reading the RTC Error Address and or the record memories.

The record memory alone could be read and evaluated to determine the status of all DUT sites, but as the sizes of most of these digital tests are very large, the approach is not practical as it would consume too much test time.

The RTC Error address memory contains the failing vector addresses up to 1K failures. The record memory for each of these addresses can then read to determine the failing DUT site(s). As each entry indicates a failing location time is not wasted reading large sections of record memory to determine the test failures. Unless the number of failures is less than 1k or all DUTs have failed as indicated above, the status of all DUTs cannot be determined. In this case the test program must disable the failing test sites and rerun the digital test until the status of all DUT test sites are known. The GtDio6x series of digital instruments provides a method to abort the test sequence if a failure is detected; this feature can save test time when a failure occurs.

 Single-Domain Per Site Solution
Table 2 – The relative merits of the Single-Domain Solution


Summary

The following table compares the two solutions:
Multisite in a Single Domain SolutionSingle Site Per Domain Solution
Programming is required to Create Digital Test FileAutomatic Generation of Digital Test File
Reduced number of PXI Slots and BoardsMore Slots/Digital Test Boards
Lower Hardware CostHigher Hardware Cost
Slower DeploymentFaster Deployment
Requires complicated programming to find the faulty DUTBetter Diagnostics
Lower Test YieldMaximum Test Yield
Table 3 – Pros and Cons of Single vs. Multiple Domain Solutions


Conclusion

Unless the space (PXI slots) in the semiconductor test system is at premium, a multi-site test system should always be designed using one digital domain for each DUT test site. The upfront costs of adding the additional hardware will pay large dividends, guarantying the fastest possible test times and simplifying test programming. Careful consideration of these capabilities is paramount in the design of a multi-site digital test system.
Article Date 2/2/2021
Keywords Multisite Digital Test, GtDio6X, GX5960, GX5926

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