Abstract: A remote I/O system includes an information network control module, I/O interface modules, and a remote I/O module. The information network control module includes a common memory and a second control IC. The second control IC includes a variation detecting circuit that includes a data latch buffer that stores read data from an information network; and a variation detection memory that stores data previously read from the information network. The variation detecting circuit compares data stored in the data latch buffer with data stored in the variation detection memory, to detect a variation in the data. The second control IC transmits, to the I/O interface module, by cyclic scan transmission, data from one of the scan memory areas corresponding to the data having the variation detected by the variation detecting circuit.

Abstract: A remote I/O system includes an information network control module, I/O interface modules, and a remote I/O module. The information network control module includes a common memory and a second control IC. The second control IC includes a variation detecting circuit that includes a data latch buffer that stores read data from an information network; and a variation detection memory that stores data previously read from the information network. The variation detecting circuit compares data stored in the data latch buffer with data stored in the variation detection memory, to detect a variation in the data. The second control IC transmits, to the I/O interface module, by cyclic scan transmission, data from one of the scan memory areas corresponding to the data having the variation detected by the variation detecting circuit.

Abstract: According to one embodiment, a signal control circuit includes a high-speed serial bus I/F circuit, a data conversion circuit, a trace circuit, and a memory arbitration circuit. The high-speed serial bus I/F circuit receives serial data from an external device by high-speed serial bus communication, and converts the serial data to parallel data. The data conversion circuit converts one of the parallel data to common data to be stored in an external memory. The trace circuit converts the other parallel data to trace data to be stored in the external memory. The memory arbitration circuit stores the common data in a common memory area of the external memory, stores the trace data in a trace memory area being different from the common memory area of the external memory, and when null is supplied from outside, does not store the trace data in the trace memory area.