TEST METHOD FOR VOLATILE MEMORY

PROBLEM TO BE SOLVED: To provide a test method for shortening a test time of a volatile memory. SOLUTION: Instaed of a conventional access test, data in which all bits are '0' of a data bus connected to a volatile memory is written in a volatile memory, only arbitrary 1 bit of a data bus connected to the volatile memory is level-changed from '0' to '1' and written in the volatile memory, states of the bits before and after of the level-change and other bits are read and state change is detected, when a state is changed, it is judged that the surrounding of the bit is defective, while defect of the surrounding of the data bus connected to the volatile memory is detected by performed the above operation for all bits of the data bus connected to the volatile memory.