A digital multilevel bit memory array system comprises regular memory arrays
and
redundant memory arrays. A regular y-driver corresponds to each memory array to
read or write contents to a multilevel bit memory cell and compare the read cell
content to reference voltage levels to determine the data stored in the corresponding
memory cell. Likewise, similar functions are performed by the redundant y-driver
circuit for the redundant memory array. During the verification of the contents
of the memory cell, if the read voltage is outside a certain margin requirement
for a level of the reference voltage, a signal is generated in real time so that
data from the bad y-driver is not output and data from the redundant y-driver corresponding
to the redundant memory array is read out. The memory array system may also include
a fractional multilevel redundancy.