| 摘要 |
PURPOSE:To lay a transmission line very easily, by transmitting output data, input data, and an abnormality signal through a transmission loop constituted with the transmission line of one system. CONSTITUTION:When one cycle of the execution of a user program is performed by a CPU3, all input/output data of an input/output memory 7 is transferred to a transmission buffer memory 10, and only input data is extracted from data in a reception buffer memory 11 and is written in the input/output memory 7. At this time point, the CPU3 starts the execution of the user program. Simultaneously, a transmitting device 8 and a receiving device 9 are operated to not only give output data in the transmission buffer memory 10 to an output unit but also take input data from an input unit and the abnormality signal from an output unit into the reception buffer memory 11 in parallel with the executing operation of the user program. Thus, a serial data line 2 is formed into a loop to transmit output/input data and the abnormality signal. |
