Test method of one chip micro-computer and one chip micro-computer for conducting the test

摘要

When testing internal state of one chip micro-computer having a CPU and a ROM installed in a single package, data D read from the ROM is subjected to non-degenerate conversion using data DT from the outside and is executed as a command code by the CPU in a test mode. To input the data DT which can serve as a correct command code from the outside, it is necessary that the data D is known. A third party is incapable of conducting a test for testing the internal state and wrongfully reading the written data.