MEMORY CONTROL METHOD

PURPOSE:To improve efficiency for processings by preventing any new data from being written onto unread data even though the processings are asynchronously executed while asynchronously executing the processing of write to a memory and the processing of read from the memory. CONSTITUTION:When a write operation is started, first of all, the positions of a read address and a write address are checked (step 21) and when the write address and the read address are not coincident, the processing of writing data to the memory is executed. When the write address and the read address are coincident, however, it is judged whether the write operation is performed for the first time or not (step 22). When the write operation is executed for the first time, the write operation is executed since no data exists in the memory even though the write address and the read address are coincident. When the write operation is not executed for the first time, the write operation is not executed but an error processing is executed since unprocessed data are destroyed when the write operation is executed in the case of not executing a read processing although data are already written in the memory.