A memory includes a set of sequentially stored data. Each of the data includes a variable-length data and length information indicative of a data length of the variable-length data. An MPU creates a read instruction for reading the set of data. A DMS chip, upon receiving the read instruction, reads length information from the memory, calculates a storage location of subsequent data in the memory, and reads the subsequent data from the first memory. Thus, the DMS chip reads the subsequent data from the memory instead of the MPU thereby reducing load on the MPU.