A read and write control circuit receives (m×n))-bit data output m-bit parallel from a D flip flop, and a q-bit data selection signal such that the output data from the D flip flop is written to memory circuits in units of integral multiples of (x+1) bits in a total of 2q operations, in accordance with a binary value indicated by the data selection signal, where m, n, x and q indicates positive integers (x+1)>m and n>2q, where m, n, x and 1 indicate positive integers and (x+1)>m and n>2q. The data written to the memory circuits is read out in units of integral multiples of (x+1) bits in a total of 2q operations.