A memory device includes a memory cell array including memory cells connected to word lines and bit lines. Each of the memory cells includes a switch element and a memory element, and has a first state or a second state in which a threshold voltage is within a first voltage range or a second voltage range, lower than the first voltage range. A memory controller is configured to execute a first read operation for the memory cells using a first read voltage, higher than a median value of the first voltage range, program first defect memory cells turned off during the first read operation to the first state, execute a second read operation for the memory cells using a second read voltage, lower than a median value of the second voltage range, and execute a repair operation for second defect memory cells turned on during the second read operation.

A comparison circuit includes a reference adjustment module, a signal receiving module, and a control module. The reference adjustment module is configured to receive a first reference signal and output a second reference signal. The reference adjustment module is further configured to receive an adjustment signal, and unidirectionally adjust the equivalent coefficient within a preset value interval when the adjustment signal is received. The signal receiving module is configured to receive the second reference signal and an external signal. The second reference signal after experiencing a mismatch of the signal receiving module is equivalent to a third reference signal. The control module is configured to: receive an enable signal and the comparison signal; and during a period of continuously receiving the enable signal, when the comparison signal jumps, terminate the output of the adjustment signal.

A memory device includes a driver that drives a data line connected with an external device, an internal ZQ manager that generates an internal ZQ start signal, a selector that selects one of the internal ZQ start signal and a ZQ start command from the external device, based on a ZQ mode, a ZQ calibration engine that generates a ZQ code by performing ZQ calibration in response to a selection result of the selector, and a ZQ code register that loads the ZQ code onto the driver in response to a ZQ calibration command from the external device.

Control logic in a memory device initiates a read operation on a memory array of the memory device and performs a calibration operation to detect a change in string resistance in the memory array. The control logic determines whether the change in string resistance is attributable to charge loss in the memory array, and responsive to determining that the change in string resistance is attributable to charge loss in the memory array, preforms the read operation using calibrated read voltage levels to read data from the memory array.

An impedance calibration circuit includes a first code generation circuit connected to a first reference resistor, and configured to generate a first code for forming a resistance based on the first reference resistor, by using the first reference resistor; a second code generation circuit configured to form a resistance of a second reference resistor less than the resistance of the first reference resistor, based on the first code, and generate a second code by using the second reference resistor; and a target impedance code generation circuit configured to generate a target impedance code based on the first code, the second code, and a target impedance value, and form an impedance having the target impedance value in a termination driver connected to the impedance calibration circuit, based on the target impedance code.

Methods, systems, and apparatuses related to memory operation with common clock signals are provided. A memory device or system that includes one or more memory devices may be operable with a common clock signal without a delay from switching on-die termination on or off. For example, a memory device may comprise first impedance adjustment circuitry configured to provide a first impedance to a received clock signal having a clock impedance and second impedance adjustment circuitry configured to provide a second impedance to the received clock signal. The first impedance and the second impedance may be configured to provide a combined impedance about equal to the clock impedance when the first impedance adjustment circuitry and the second impedance adjustment circuitry are connected to the received clock signal in parallel.

A semiconductor device includes a controller circuit and a signal generating circuit. The controller circuit is coupled to a plurality of memory devices and configured to generate a plurality of chip enable signals. One of the chip enable signals is provided to one of the memory devices, so as to respectively enable the corresponding memory device. The signal generating circuit is disposed outside of the controller circuit and configured to receive the chip enable signals and generate a termination circuit enable signal according to the chip enable signals. The termination circuit enable signal is provided to the memory devices. When a state of any of the chip enable signals is set to an enabled state, a state of the termination circuit enable signal generated by the signal generating circuit is set to an enabled state.

An electronic device includes an enable signal generation circuit configured to activate, when a write operation is performed, a termination enable signal earlier than a time point when a write latency elapses, by a duration amount of an entry offset period; and a data input and output circuit configured to receive, when the write operation is performed, data later than the time point when the write latency elapses, based on the termination enable signal, wherein the data input and output circuit receives the data after the write latency elapses by a duration amount of a first data reception delay period.

A memory device includes a cell array including a memory cell that includes a variable resistance element, a reference resistor configured to provide a resistance varying according to an adjustment code, and a read circuit configured to read data that is stored in the memory cell, based on a resistance of the variable resistance element and the resistance of the reference resistor. The memory device further includes a reference adjustment circuit configured to obtain a first calibration code corresponding to a temperature variation, and a second calibration code corresponding to a process variation, and perform an arithmetic operation on the obtained first calibration code and the obtained second calibration code, to obtain the adjustment code.

An electronic device includes an enable signal generation circuit configured to activate, when a write operation is performed, a termination enable signal earlier than a time point when a write latency elapses, by a duration amount of an entry offset period; and a data input and output circuit configured to receive, when the write operation is performed, data later than the time point when the write latency elapses, based on the termination enable signal, wherein the data input and output circuit receives the data after the write latency elapses by a duration amount of a first data reception delay period.