AUTOMATED TEST


BEST PRACTICES FOR USER-PROGRAMMABLE FPGA INSTRUMENTATION


By Mike Dewey


Field programmable gate arrays (FPGAs) are used extensively in


today’s electronic assemblies and test engineers are also choosing to incorpo- rate user-programmable FPGA instru- mentation as part of their functional test solutions. Today there are a variety of user-programmable FPGA-based instru- ments available to test engineers that can be used to support a wide range of applications and interfaces. Tese mod- ules, which allow test engineers to create custom instrumentation and interfaces, employ a range of programming tools and architectures. Depending on the complexity of this custom instrument, the design, integra- tion, and supportability can prove chal- lenging and demanding for test engineers. However, by adhering to industry standards for design tools and employing standardized FPGA interfaces, the complexity and ef- fort required to design, deploy, and maintain these modules as part of a test system can be mitigated.


Background


FPGAs were an outgrowth of the programmable array logic (PAL) business in the late 1970s. These devices enabled design engineers to r place discrete logic chips with one pro- grammable chip. FPGAs emerged in the 1980s as a common logic design compo- nent, with Xilinx and Altera becoming the market leaders.


re-


Today’s FPGAs offer multiple pro- cessing cores which can run in parallel, allowing different tasks to be executed within separate “blocks” of the FPGA. Within the FPGA are a number of pre- defined resources which include a number


A. SFigure 2. FPGA design / deployment process 18 EVALUATION ENGINEERING JANUARY 2019


of logic blocks, both configurable and fixed-function, as well as internal memory. In addition, modern FPGAs have evolved into SoC (system on chip) devices—offering higher levels of func- tionality including: • Signal processing blocks • Embedded processors • Cache memory • High speed serial input/ output I/O


• Graphical processing units (GPU)


• Video codecs • Mixed-signal support


SFigure 1. User-programmable FPGA module with I/O adapter board


Today, these FPGAs are incorporated into card modular products for a range of platforms including cPCI, VME, VPX, and PXI. With a user-programmable, FP- GA-based test instrument such as a card modular PXI module (Figure 1), the test engineer can implement test solutions using commercially avail- able IP (Intellectual Property) cores or in-house developed, custom IP— essentially creating his or her own custom instrument by programming the module for the specific applica- tion. With the ability to design and program an instrument for specific applications, test engineers have the flexibility to support not only a cur- rent product, but also future prod- ucts that might require a specialized instrument or interface.


FGPA Design Tools & Methods Suppliers of FPGAs and FPGA modules offer tool sets that are optimized for supporting their own specific product offerings. Te overall design process for an FPGA is detailed in Figure 2 to the left.


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