| 摘要 |
PURPOSE:To make a code error check on respective bits of the process input and output signals of a CPU and improve the reliability by providing a tri-state inversion input buffer, and inverting the respective bits in logical level. CONSTITUTION:When the CPU1 inputs the process input signal 5, the signal is written in input memories 36 and 37 through an input converting circuit 35 firstly. An input device 3 sends out the contents of the memory 36 to the CPU1, which receives and stores them and then indicates inversion input. A tri-state inversion input buffer 39 inverts the respective bits of the contents of the memory 37 in logical level and sends out a data signal 23 to the CPU1. The CPU1 checks on the logical states of corresponding bits of this signal 23 and said received and stored signal. Further, when the CPU1 outputs a process output signal 6, its respective bits are checked through a tri-state inversion input buffer 48. Consequently, a code error is detected as to every bit and the reliability is improved. |
