A test device for an SoC test architecture has a test input port, a test output port, a plurality of cores, a register, and a plurality of user defined logics. The register has a plurality of bits corresponding to the cores. Each of the user defined logics is connected to a corresponding bit of the register and a corresponding one of the cores. Each of the user defined logic receives a plurality of test control signals, and receives the corresponding bit of the register to change values of the test control signals. Outputs of each of the user defined logics are connected to the corresponding core to determine whether a test instruction of the corresponding core is or is not needed to be updated.