Patent ID: 6917835

Claim:
A programmable logic controller system comprising: a) a CPU unit which comprises: a memory for storing information on expansion units separately for each expansion unit, wherein the information includes at least information representing a corresponding expansion unit ID number and type, and wherein the information on each of the expansion units contains various setup values of the expansion units, and wherein the memory stores screen configuration information that corresponds to each type of expansion unit, and wherein the information of the expansion units includes a parameter whose setup value is changeable; a display for displaying the information on the expansion units stored in the memory; and an operation key for selecting the information displayed on the display, wherein when an operation key is activated, the setup values of the selected expansion unit are displayed on the display and are changeable, and when changed, the changed setup values are stored in the memory; and b) a plurality of expansion units, including al least one I/O unit, wherein at least two of the expansion units are different in type from one another, and which are connected to the CPU unit, wherein each of the expansion unit comprises: a selection button, disposed on each of the expansion units, for selecting one of the expansion units, wherein information corresponding to a selected expansion unit is read from the memory and the information read is displayed on the display based on the screen configuration information corresponding to the selected type of expansion unit.