PURPOSE: To improve practicality by waiting for the access of high order data for prescribed time even when another low order word is accessed after the certain low order word.

CONSTITUTION: This system 15 provided with respective timers 4a-4c for measuring access limit time by measurement start signals and outputting access error signals when measurement completion signals are not received within the access limit time, a word address memory 3a for storing word address information and a doubleword judging circuit 3 for judging whether or not the address information of the low order word corresponding to the access request of the certain word is stored in the word address memory 3a when the request comes from a CPU 1 to a doubleword memory 2, storing the address information of the certain word in the word address memory 3a and sending out the measurement start signals to the idle timer waxen a judged result indicates that it is 'not stored' and sending out the measurement completion signals to the pertinent timer when the judged result indicates that it is 'stored'.