22.214.171.124. SEU Sensitivity Processing
Reconfiguring a running FPGA has a significant impact on the system using the FPGA. When planning for SEU recovery, account for the time required to bring the FPGA to a state consistent with the current state of the system. For example, if an internal state machine is in an illegal state, it may require reset. In addition, the surrounding logic may need to account for this unexpected operation.
Often an SEU impacts CRAM bits not used by the implemented design. Many configuration bits are not used because they control logic and routing wires that are not used in a design. Depending on the implementation, 40% of all CRAM bits can be used even in the most heavily utilized devices. This means that only 40% of SEU events require intervention, and you can ignore 60% of SEU events. The utilized bits are considered as critical bits while the non-utilized bits are considered as non-critical bits.
You can determine that portions of the implemented design are not utilized in the FPGA’s function. Examples may include test circuitry implemented but not important to the operation of the device, or other non-critical functions that may be logged but do not need to be reprogrammed or reset.
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