A method includes generating a first edge of a first tracking signal for a tracking cell, generating a first edge of a second tracking signal for the tracking cell based on the first edge of the first tracking signal, generating a first edge of a cell signal for a memory cell, generating a second edge of the first tracking signal based on the first edge of the second tracking signal, and generating a second edge of the cell signal based on the second edge of the first tracking signal. A transistor in the tracking cell operates at a tracking voltage value and a transistor in the memory cell operates at a memory voltage value different from the tracking voltage value.