Multi-context-scrubbing operation for a 1-bit counter circuit

Since space embedded systems used for space rockets, space stations, and space satellites are constantly affected by radiation, high soft-error tolerant devices are absolutely necessary. Currently, although field programmable gate arrays (FPGAs) are used widely for such space systems, the configuration memory is extremely vulnerable to radiation. Therefore, scrubbing methods are applied frequently for the FPGA configuration memory to increase their soft-error tolerance. This paper presents a proposal of a multi-context scrubbing method applicable for sequential circuits on a radiation-hardened optically reconfigurable gate array. The scrubbing operation can be executed within a $1 \mu \mathrm{s}$ period, which is about 100,000 times faster than that of existing FPGAs. Moreover, a system protected by the scrubbing operation can function with no termination, even after some flip-flops are permanently ruined by radiation.