SRAM-based FPGA's: testing the LUT/RAM modules

  • Authors:
  • Michel Renovell;J. M. Portal;J. Figueras;Yervant Zorian

  • Affiliations:
  • -;-;-;-

  • Venue:
  • ITC '98 Proceedings of the 1998 IEEE International Test Conference
  • Year:
  • 1998

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Abstract

This paper addresses the problem of testing theLUT/RAM modules of configurable SRAM-based FPGAs usinga minimum number of test configurations. A model ofarchitecture for the LUT/RAM module with N inputs and 2Nmemory cells is proposed taking into account the LUT andRAM modes.Concerning the RAM mode, we demonstrate that a unique testconfiguration is required for a single module. The problem isshown equivalent to the test of a classical SRAM circuitallowing to use existing algorithms such as the march tests. Wealso propose a unique test configuration called pseudo shiftregister' for an mxm arrays of modules. In this configuration,the circuit operates as a shift register and an adapted version ofthe MATS++ algorithm called shifted MATS++' is described.Concerning the LUT mode, we use the concept of non-redundanttest that proposes to test in LUT mode the parts ofthe module not tested in RAM mode. Under this hypothesis, it isdemonstrated that the test of a single module as well as the testof an mxm array of modules require only 3 test configurations.Using our solution, the test of a complete array of mxmLUT/RAM modules requires 4 test configurations independentlyof the size of the array and of the modules.