ROM TESTING DEVICE AND ROM TESTING SYSTEM

PURPOSE:To detect abnormality in the contents of a ROM by successively reading out the stored contents for a prescribed unit, comparing the contents of the preceding and following units so as to decide the degree of a change and comparing the result of deciding the change degree with a threshold value. CONSTITUTION:A control part 37 controls a read part 21, reads out the first byte of a ROM 11, stores it in a first storage part 23, next moves the contents of the first storage part 23 to a second storage part 25, reads out the next byte of the ROM 11, stores it in the first storage part 23 and stores the data of the continuous bytes of the ROM 11 in the first and second storage parts 23 and 25. A comparator 27 compares the respective contents of the first and second storage parts 23 and 25, compares the change degree decided result showing the degree of the change with the threshold value and decides the ROM 11 is abnormal in the case of the small change degree based on a fact that the value exceeds a prescribed value when the contents of the ROM 11 are normal. Thus, the abnormality in the ROM 11 can be detected.