The scrubbing rate depends on failure intensity and desired reliability. The approximate equation to determine the LMB memory scrubbing rate in this case is given by:
PW =
760 ( BER2 / SR2 )
Where PW is the probability of an uncorrectable error in a memory word, BER is the soft error rate for a single memory bit, and SR is the scrubbing rate.
The soft error rates affecting block RAM for each product family can be found in the Device Reliability Report (UG116).