Abstract: An application specific integrated circuit that comprises a central processing unit and a plurality of devices which are dependent on the application of the integrated circuit and are connected to the central processing unit. At least one shift register is provided by connecting in series elementary cells each mounted on a respective line corresponding to an input/output line of the central processing unit, each cell being able to inject into its respective line a value entered serially through the shift register, and further being able to sample the value of the binary signal carried by its respective line with a view to a reading of this value through the shift register. A method is provided for using the shift register to test the makeup of the application specific integrated circuit, or an application program executing on the central processing unit.