A system controller exchanges data with a memory controller. The system controller includes an interpreting unit, a first instruction data supplying unit, a second instruction data supplying unit, and a controlling unit. The second instruction data supplying unit transfers the first operation instruction data provided from a host system to the memory controller. If the interpreting unit interprets the first operation instruction data as data instructing to begin an operation with the second instruction data supplying unit, the controlling unit shifts to a first mode that halts the first instruction data supplying unit and that begins an operation with the second instruction data supplying unit.