SRAM-based FPGAs: Testing the embedded RAM modules

This paper addresses the problem of testing the RAM mode of the LUT/RAM modules of configurable SRAM-based Field Programmable Gate Arrays (FPGAs) using a minimum number of test configurations. A model of architecture for the LUT/RAM module with N inputs and 2N memory cells is proposed taking into account the LUT and RAM modes. Targeting the RAM mode, we demonstrate that a unique test configuration is required for a single module. The problem is shown equivalent to the test of a classical SRAM circuit allowing to use existing algorithms such as the March tests. We also propose a unique test configuration called 'pseudo shift register' for an m x m array of modules. In the proposed configuration, the circuit operates as a shift register and an adapted version of the MATS++ algorithm called 'shifted MATS++' is described.