Data verification in a memory device using a portion of a data retention
margin is provided. A bit count is read from the region to determine
whether errors will result in the memory. A read in one or more retention
margin portions is performed after the normal program verify sequence and
if the number of bits in these regions is more than a pre-set the memory
will fail verify status. A method of verifying data in a memory device
includes the steps of: defining an retention margin between adjacent data
thresholds; programming the memory device with data; determining whether
bits are present in the data retention margin; and if the number of bits
in the retention margin exceeds a threshold, generating an error.