Semiconductor device test system with test interface means

A semiconductor device test system has an interface for use with a semiconductor device test method, and a semiconductor device test method. In a first mode of an interface, in reaction to test signals corresponding to a test standard, for example, a JTAG test standard, and received by the interface from a test device, the interface outputs signals corresponding to the test standard to a semiconductor device to be tested. In a second mode of the interface, in reaction to test signals corresponding to the test standard and received by the interface from a test device, the interface outputs signals that do not correspond to the test standard to a semiconductor device to be tested.