To enhance a read speed for character data and reduce a load in reading the character data.

A halfway point of a data bus 16 is branched to two systems (22, 26) and, a first buffer 21 and a second buffer 25 are interposed in the first system data bus 22 and the second system data bus 26 respectively. The first buffer 21 is connected to the first system data bus 22 with an input bit order and an output bit order of the first buffer 21 being agreed. Moreover, an input bit order of the second buffer 25 is made opposite to the input bit order of the first buffer 21 while an output bit order of the second buffer is made the same as the output bit order of the first buffer 21 when the second buffer is connected to the second system data bus 26. Either one and the other of the first buffer 21 and second buffer 25 can be selected and switched on and off in the constitution.