| 摘要 |
PURPOSE:To make it possible to prevent the execution of an improper instruction, by providing methods of discriminating, checking and detecting whether write or read information is an instruction word or data word. CONSTITUTION:During a write from CPU1 to memory unit 2, signals of ''0'' for an instruction word and ''1'' for a data word are transmitted as the 1st control signals to parity-bit generating method 12 via the 1st sending method 11. In method 12, parity bits are added to the instruction word and data word by the 1st control signal with the both opposite in parity, and then stored in memory unit 2. At the time of a read from unit 2, parity-checking method 14 outputs to improper-word detecting method 15 a signal of ''0'' when the parity of the read word is odd and a signal of ''1'' when even. Method 15 detects an improper word by the signal from method 14, and the 2nd control singal from the 2nd sending method 13 indicating that the instruction word is ''1'' and the data word is ''0'', and if it is found, the read of words to CPU1 is stopped via gate control method 16. |
