Sensing memory cells can include: applying a voltage ramp to a group of memory cells to sense their respective states; sensing when a first switching event occurs to one of the memory cells responsive to the applied voltage ramp; stopping application of the voltage ramp after a particular amount of time subsequent to when the first switching event occurs; and determining which additional memory cells of the group experience the switching event during the particular amount of time. Those cells determined to have experienced the switching event responsive to the applied voltage ramp are sensed as storing a first data value and those cells determined to not have experienced the switching event responsive to the applied voltage ramp are sensed as storing a second data value. The group stores data according to an encoding function constrained such that each code pattern includes at least one data unit having the first data value.