A receiving portion 2e for rotatably receiving therein a planetary gear 3, is formed between a plurality of retaining protrusions 2d of a carrier. The core block generates core internal data responsive to output data from the input ports and is configured to output the core internal data during scan testing and to selectively generate core output data for the output ports responsive to the core internal data or to test vector serial input data from the vector input terminal. A data selection circuit selects mn pieces of data at a time and a data output section outputs these pieces of data to an external data bus of a width of L=mn bits.