OLT(RE)2: An On-Line On-Demand Testing Approach for Permanent Radiation Effects in Reconfigurable Systems

Reconfigurable systems gained great interest in a wide range of application fields, including aerospace, where electronic devices are exposed to a very harsh working environment. Commercial SRAM-based FPGA devices represent an extremely interesting hardware platform for this kind of systems since they combine low cost with the possibility to utilize state-of-the-art processing power as well as the flexibility of reconfigurable hardware. In this paper we present OLT(RE)²: an on-line on-demand approach to test permanent faults induced by radiation in reconfigurable systems used in space missions. The proposed approach relies on a test circuit and on custom place and route algorithms. OLT(RE)² exploits partial dynamic reconfigurability offered by today's SRAM-based FPGAs to place the test circuits at run-time. The goal of OLT(RE)² is to test unprogrammed areas of the FPGA before using them, thus preventing functional modules of the reconfigurable system to be placed on areas with faulty resources. Experimental results have shown that (i) it is possible to generate, place and route the test circuits needed to detect on average more than 99 percent of the physical wires and on average about 97 percent of the programmable interconnection points of an arbitrary large region of the FPGA in a reasonable time and that (ii) it is possible to download and run the whole test suite on the target device without interfering with the normal functioning of the system.

I. Introduction

The interest in employing FPGA-based reconfigurable systems in space applications is growing more and more  [1]–[3]. Several reconfigurable systems are going to be launched in space in the next few years, e.g., the Polarimetric and Helioseismic Imager Data Processing Unit that will be hosted on the ESA Solar Orbiter  [4] (launch planned in 2018) and the Fraunhofer On-Board Processor (FOBP)  [5] (launch planned in 2020). These very expensive projects rely on high-end radiation-hardened mature FPGA devices with very high costs and lower performance compared with the latest commercial FPGAs. On the other hand, today's commercial SRAM-based FPGA devices represent the most interesting technological platform for research projects that need high performance and low cost at the same time. Such devices provide a significantly larger amount of resources and they can be dynamically and partially reconfigured, thus allowing performance increase, energy efficiency improvement, and fault tolerance enhancement  [6]. Moreover, such devices are significantly cheaper than radiation hardened ones.