PURPOSE: To attain comparatively high speed data transfer and to decrease the occupied time of an internal common bus by patterning a byte arranging conversion of a data and applying arranging conversion.

CONSTITUTION: The number of conversions of byte location by conversion pattern is selected as 4 patterns, and when the conversion pattern 1 is used, for example, the 1st transfer to a storage section 3-2 is 3-byte and a byte mark '0111' is added. When the transfer is finished, the remaining 1-byte is moved from a buffer register BFR to a DBR, no transfer to the storage section 3-2 is applied, the next 1 word is received from a main storage device 2 and set to the buffer register BFR. The 3 bytes of the buffer register BFR is moved to the DBR and when 4-byte (1 word) is obtained, a byte mark '1111' is added and the result is transferred to the storage section 3-2. Similarly, the byte conversion control between the buffer registers BFR and DBR is executed.