This paper describes the implementation of a SoC(System-on-a-Chip) and an ISDN communication terminal by the SoC in ISDN network. The SoC has been developed with the functions of 32-bit ARM7TDMI RISC core processor, network connection with S/T interface, TDM--bus interface and voice codec, user interface. And we also review the developed software structure and the ISDN service protocol procedures which are working on the SoC. And finally this paper describers a structure of an ISDN terminal equipment using the implemented SoC and terminal software.