PROGRAMMABLE CONTROLLER

PURPOSE:To decrease the number of instruction keys and to facilitate an easy operation of a programmable controller by providing an instruction key which can be used for both an operation code and an operand of a user instruction to a user program input device of a programmable controller. CONSTITUTION:An L key 67 is provided to a panel of a user program input device of a programmable controller. This key 67 can be used bor both cases where the arithmetic result is inverted with an operation code and an input is inverted with an operand respectively. The contents of an accumulator are inverted with an instruction L if given in an instruction decoding mode. If the instruction is equal to an AND and the 3rd operand is equal to L, the contents of the accumulator and a buffer register are inverted and multiplied by each other and then stored again to the accumulator. Thus an operation code and an operand code are used for discrimination and execution of L.