Testing the Interconnect of RAM-Based FPGAs

  • Authors:
  • Michel Renovell;Jean Michel Portal;Joan Figueras;Yervant Zorian

  • Affiliations:
  • -;-;-;-

  • Venue:
  • IEEE Design & Test
  • Year:
  • 1998

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Abstract

Programmable logic in the form of field-programmable gate arrays has become a widely accepted design approach for low- and medium-volume computing applications. Low development costs and inherent functional flexibility have spurred the spectacular growth of this technology. FPGAs are regular structures of logic modules communicating via an interconnect architecture of lines and switches. Users program the logic modules and interconnect structures to perform particular functions and realize the FPGA's global function.Manufacturers provide programmability in their FPGA architectures in various ways. They may use RAM to store configuration information, EPROM switches based on FAMOS (floating-gate avalanche-injection metal oxide semiconductor) transistors and fuses, or antifuses that permanently open or close connections. Of these alternatives, we have focused our work on RAM-based FPGAs. Their simplicity and flexibility for user changes in the field make this type of FPGA a very popular choice among designers. The architecture and design of these devices have been widely investigated during the last decade, but their test challenges have received less attention. Only recently have researchers addressed the problem of testing after manufacture-in other words, before user programming of specific functions. Testing before programming presents a wide spectrum of problems, for which a number of researchers have proposed innovative solutions.Testing an FPGA chip poses a challenging problem for test engineers. It requires implementing various configurations (programmings) of the FPGA. But changing configurations incurs reprogramming costs. So the question arises: How can we determine the minimum number of test configurations and corresponding vector test sequences that will cover all the faults of an FPGA's structural fault model? Dealing with this question in an earlier work, we proposed a general methodology for test configuration and test pattern generation. 5 Here, we apply this methodology to the interconnect structure. We propose a manufacturing test procedure for RAM- based FPGA interconnect structures.