In this paper, we describe the formal verification methodology used for the AMBA AXI Port Interface (XPI) controller of the Synopsys DesignWare Cores DDR Memory Controller. The controller is feature-rich and the XPI is a highly configurable design, which varies with both hardware and software configuration parameter settings. This creates a formidable challenge for traditional verification methods as there are many combinations of settings resulting in long simulation cycles to reach the coverage objectives. Contrast this with formal verification, which uses mathematical algorithms to efficiently test design behaviors for all possible stimulus and configurations. We will describe the formal verification flow including configurable formal testbench implementation and formal coverage closure.