Programmable logic device (PLD) with memory refresh based on single event upset (SEU) occurrence to maintain soft error immunity

摘要

A Programmable Logic Device (PLD) is provided with configuration memory cells displaying a superior soft error immunity by combating single event upsets (SEUs) as the configuration memory cells are regularly refreshed from non-volatile storage depending on the rate SEUs may occur. Circuitry on the PLD uses a programmable timer to set a refresh rate for the configuration memory cells. Because an SEU which erases the state of a small sized memory cell due to collisions with cosmic particles may take some time to cause a functional failure, periodic refreshing will prevent the functional failure. The configuration cells can be DRAM cells which occupy significantly less space than the SRAM cells. Refresh circuitry typically provided for DRAM cells is reduced by using the programming circuitry of the PLD. Data in the configuration cells of the PLD are reloaded from either external or internal soft-error immune non-volatile memory.