"Availability Analysis of Xilinx FPGA on Orbit"
National Institute of Information and Communications Technology
This paper will discuss availability of reconfigurable devices on orbit. To compose satellite mission equipment with reconfigurable devices is very attractive because that a newly function can be implemented on the equipment after launching. It is well known, however, that the devices are very weak against radiation effects, and the circuit that configured by a software will be changed by a single event upset (SEU).
It is very important to consider about availability, if the equipment will be used for commercial services. Very high availability or low non-availability is required for the consumer communications market. A typical non-availability value for terrestrial network equipment is 10E-6. If a SEU occurs on the reconfigurable device, the device should be rebooted. During rebooting process, the device can not work and not provide the service. If the SEU can be defined as a accidental failure and the failure can be fixed without any loss of the original device function, the rebooting process also can be defined as a repairing. Then, a mean time to repairer (MTTR）and a mean time before failure (MTBF) is just same as a time needed for rebooting and a SEU frequency. The nonavaiability can be obtained from the MTTR and the MTBF.
We have already tested two types of FPGA that belong to the same product line (XC2VP4 and XC2VP7). The result showed that the SEU frequency depend on the size of their configuration data size. All the download data rates of Xilinx FPGA that belong to the same line are identical (e.x. 50M byte/second for XC2V series). Therefore, a large scale FPGA device has large MTTR compared with a small size device. Moreover, since the SEU frequency depends on the size, the large device also has large MTBF. A simple numerical analysis and evaluation of the nonavailability will be shown in this paper. And it will be also shown that the nonavailability for large scale circuit can be lowered by using multiple small devices.
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