A method of controlling a memory and a memory controller are disclosed. The memory controller is operable to control a memory, the memory being operable in a plurality of modes, the memory controller comprising: memory interface logic configurable to interact with the memory in each of the plurality of modes; and memory mode change logic operable, in response to a memory mode change request instruction specifying a predetermined one the plurality of modes being issued by the memory interface logic to the memory, to request the memory interface logic to be configured to interact with the memory in the predetermined one of the plurality of modes and to prevent interaction between the memory interface logic and the memory until the memory interface logic confirms that it is configured to interact with the memory in the predetermined one of the plurality of modes. In this way, it will be appreciated that both the memory and the memory controller can be reconfigured to operate in a different mode using a single instruction which provides performance benefits, increases reliability and reduces infrastructure requirements.