Evaluating SEU Sensitivity of Virtex Configuration Logic Registers

Radiation induced failure modes of the Virtex I family have already been analyzed in the past. About configuration logic in particular, at least three kinds of Single Event Functional Interrupts (SEFIs) were believed to exist in the Virtex I, as a consequence of Single Event Upsets [1]: 1) JTAG TAP controller upset; 2) configuration control state machines reset (FSM POR SEFI); 3) SelectMAP configuration pin upsets. The literature reports about SEFIs occurred during a heavy-ion dynamic radiation test, whose detected effect was the complete loss of device configuration, resulting in a huge number of bits being misread. The corresponding cross-section measured was about 10 cm [2, 3]. This is one of the few data ever published on the Single Event Upset sensitivity for configuration logic of these devices. We previously reported about a heavy-ion radiation test on Virtex I devices, aimed at analyzing failure mechanisms of the configuration process. We measured the cross section for newly defined failure categories [4]. For one category, called Configuration Failure, we measured a saturation cross section of ≈ 1×10 cm that confirmed results already known from the literature. For the other, called Configuration & Abort Sequence Failure, the measured saturation cross section was ≈ 3×10 cm, never reported before. The probability of this error is quantitatively five orders of magnitude lower than the probability of an SEU in the configuration memory. Yet, it represents a serious hazard for scrubbing, as it might impair partial configuration ability. In an earlier study we successfully used fault injection and obtained preliminary results about SEU susceptibility of configuration control registers of Virtex I devices [5]. III. EXPERIMENTAL SET-UP