Methods, systems, and devices for varying-polarity read operations for polarity-written memory cells are described. Memory cells may be programmed to store different logic values based on applying write voltages of different polarities to the memory cells. A memory device may read the logic values based on applying read voltages to the memory cells, and the polarity of the read voltages may vary such that at least some read voltages have one polarity and at least some read voltages have another polarity. The read voltage polarity may vary randomly or according to a pattern and may be controlled by the memory device or by a host device for the memory device.

A non-volatile memory includes a cell array, a current supply circuit, a path selecting circuit and a judging circuit. The cell array includes plural multi-level memory cells in an m×n array. The cell array is connected with m word lines and n lines. The current supply circuit provides one of plural reference currents according to a current control value. The path selecting circuit is connected with the current supply circuit and the n bit lines. The judging circuit is connected with the path selecting circuit, and generates n output data. A first path selector of the path selecting circuit is connected with a path selecting circuit and a first bit line. A first judging device of the judging circuit is connected with the first path selector and generates a first output data.

Concurrent access of multiple memory cells in a cross-point memory array is disclosed. In one aspect, a forced current approach is used in which, while a select voltage is applied to a selected bit line, an access current is driven separately through each selected word line to concurrently drive the access current separately through each selected memory cell. Hence, multiple memory cells are concurrently accessed. In some aspects, the memory cells are accessed using a self-referenced read (SRR), which improves read margin. Concurrently accessing more than one memory cell in a cross-point memory array improves bandwidth. Moreover, such concurrent accessing allows the memory system to be constructed with fewer, but larger cross-point arrays, which increases array efficiency. Moreover, concurrent access as disclosed herein is compatible with memory cells such as MRAM which require bipolar operation.

Circuits, systems, and methods for double-polarity reading of double-polarity stored data information are described. In one embodiment, a method involves applying a first voltage with a first polarity to a plurality of the memory cells. The method involves applying a second voltage with a second polarity to one or more of the plurality of memory cells. The method involves detecting electrical responses of the one or more memory cells to the first voltage and the second voltage. The method also involves determining a logic state of the one or more memory cells based on the electrical responses of the one or more memory cells to the first voltage and the second voltage.

Apparatuses, methods, and systems for sensing two memory cells to determine one data value are described herein. An embodiment includes a memory having a plurality of memory cells and circuitry configured to sense memory states of each of two memory cells to determine one data value. One data value is determined by sensing the memory state of a first one of the two memory cells using a first sensing voltage in a sense window between a first threshold voltage distribution corresponding to a first memory state and a second threshold voltage distribution corresponding to a second memory state and sensing the memory state of a second one of the two memory cells using a second sensing voltage in the sense window. The first and second sensing voltages are selectably closer in the sense window to the first threshold voltage distribution or the second threshold voltage distribution.

A disclosed example to reduce a threshold voltage drift of a selector device of a memory cell includes providing an applied voltage to the selector device of the memory cell, the applied voltage being less than a threshold voltage of the selector device, and reducing the threshold voltage drift of the memory cell by maintaining the applied voltage at the selector device for a thresholding duration to activate the selector device.

A method for reading memory cells is described. The method may include applying a first read voltage to a plurality of memory cells, detecting first threshold voltages exhibited by the plurality of memory cells in response to application of the first read voltage, associating a first logic state to one or more cells of the plurality of memory cells, applying a second read voltage to the plurality of memory cells, where the second read voltage has the same polarity of the first read voltage and a higher magnitude than an expected highest threshold voltage of memory cells in the first logic state, and detecting second threshold voltages exhibited by the plurality of memory cells in response to application of the second read voltage, among other aspects. A related circuit, a related memory device and a related system are also disclosed.

According to one embodiment, a memory controller of a memory system includes a command issuing unit, a decoder, a counter, and a statistical processor. The command issuing unit issues a first command for single read of first data from a nonvolatile memory. The decoder performs first error correction on the read first data. The counter counts a number of times of multiple reads. The statistical processor performs statistical processing of results of the multiple reads, and outputs second data obtained by the statistical processing. When the decoder is unable to perform the first error correction on the read first data, the command issuing unit issues a second command for multiple reads of the first data.

Disclosed are methods, systems and devices for generation of a read signal to be applied across a load for use in detecting a current impedance state of the load. In one implementation, a voltage and current of a generated read signal may be controlled so as to maintain a current impedance state of the load.

A memory device includes a first line coupled to a first terminal of a first memory cell, a second bit line coupled to a first terminal of a second memory cell, a sense amplifier coupled to a second end of the first bit line and a second end of the second bit line, a capacitor including a first terminal coupled to a first input of the sense amplifier and a second terminal coupled to a switch. The switch couples the second terminal of the capacitor to the second bit line during a calibration phase of a read operation and to the first bit line during a sense phase of the read operation. A current/voltage source drives current on the first bit line while the second line is floating during the calibration phase, and drives current on the second bit line while the first bit line is floating during the sense phase.