A variable resistance memory cell is read by a sense amplifier but without
rewriting the contents of the memory cell. If the memory cell has an
access transistor, the access transistor is switched off to decouple the
cell from the bit line after a predetermined amount of time. The
predetermined amount of time is sufficiently long enough to permit the
logical state of the cell to be transferred to the bit line and also
sufficiently short to isolate the cell from the bit line before the sense
amplifier operates. For memory cells which do not utilize an access
transistor, an isolation transistor may be placed in the bit line located
between and serially connection the portion of the bit line from the
sense amplifier to the isolation transistor and the portion of the bit
line from the isolation transistor to the memory cell. The isolation
transistor, normally conducting, is switched off after the predetermined
time past the time the bit line begins to discharge through the memory
cell, thereby isolating the memory cell from the sense amplifier before a
sensing operation begins.