US Patent 10348527 Testing impedance adjustment

Methods of operating integrated circuit devices include generating a voltage level at a particular node in response to a first voltage level applied to a termination device and a second voltage level applied to a reference resistance; determining whether a plurality of available resistance values of the termination device satisfy a criterion that each available resistance value is either less than a resistance value of the reference resistance, or each available resistance value is greater than the resistance value of the reference resistance; and, when the plurality of available resistance values of the termination device satisfy the criterion, determining whether a voltage level generated at the particular node for a particular available resistance value of the plurality of available resistance values is between a voltage level of a first reference voltage and a voltage level of a second reference voltage.