JPS6430255A - Large scale integrated circuit provided with failure detection circuit - Google Patents

Abstract

PURPOSE:To enable the detection of failures by using failure detecting patterns already in existence by a method wherein a plurality of input and output switching circuits is provided and the switching circuits are placed in a test mode for the connection of each of internal integrated circuits to external terminals. CONSTITUTION:Input and output switching circuits may be switched, by selecting proper input pins, between a normal mode and each of the test modes 1, 2, and 3, respectively for integrated circuits A14, B15, and C16. In an input switching circuit 3 and 3', when on a normal mode, a connection natural to the entire circuit is established. On a test mode 1, a test pattern is inputted directly to the integrated circuit A14. On a test mode 2 or 3, a test pattern is inputted, through the input switching circuit 3, into the integrated circuit B15 or, through an external input terminal 1 and the input switching circuit 3', into the integrated circuit C16. In an output switching circuit 4, when on a normal mode, a connection is established natural in the entire circuit and, on test modes 1, 2, and 3, test patterns out of the integrated circuits A14, B15, ad C16 are supplied to an external output terminal 2. In this way, a large scale integrated circuit 13 is allowed to perform its natural function when on the normal mode and, when on a test mode, to detect failures if any in the respective integrated circuits A14, B15, and C16.