To provide a counter which can receive and store the external initialization data without using any communication port.

This counter includes an input/output part 12 and a one-chip microcomputer 11. The part 12 inputs the count input, reset input and count inhibition input. Then the microcomputer 11 sets the operation of the counter in a communication mode if the reset input and the count inhibition input consist of a 1st prescribed combination among those signals which are inputted via the part 12, analyzing the subsequent count input as a function code and its data to store the data based on the analysis result and shifting automatically the operation mode to a communication mode when the reset input and the count inhibition input consist of a 2nd prescribed combination.