1. Field of the Invention
This invention relates to integrated circuit (IC) devices. Embodiments of the invention are applicable to and suitable for electronic equipment such as television receivers, video tape recorders (VTR's) and audio tape recorders, whose internal circuits are digitally controlled.
2. Description of the Prior Art
Video or audio equipment such as digital signal processing television receivers, VTRs and audio tape recorders have recently been commercialized. Most of such digital equipment uses internal bus lines common to a central processing unit (CPU), a memory, and other control circuitry. The CPU fetches control signal values for each circuit of the electronic equipment and stored in the memory, which may be a read only memory (ROM), during the normal operation and sends the fetched data to the appropriate circuit via the internal bus, which may comprise or include a so-called serial inter-integrated circuit (I.sup.2 C) bus, so as to control the operation of the internal circuit. In addition, the CPU may control the circuits in the equipment in direct response to signals supplied manually through an external keyboard or a remote controller.
Such an internal bus is conventionally either of the two-wire or three-wire type. A two-wire internal bus comprises a data transmission line and a clock transmission line. The two-wire type bus may utilize the communication system disclosed in European Patent Application No. 81201168.2 (0 051 332). On the other hand, a three-wire bus comprises a data transmission line, a clock transmisssion line, and a so-called ident signal line used to identify the nature of each data block coming over the data transmission line.
If standardized, centralized and simplified testing of the internal circuitry during assembly and servicing of such electronic equipment in which internal bus lines are installed were possible, an overall cost reduction including a reduction in manufacturing cost could be achieved.