| 摘要 |
For a microcomputer which consists of a microprocessor (CPU), input and output chips (ET, AT), at least one system memory (SSR) and a status memory (ZR), a test circuit is provided. This circuit has the task of providing the information of the internal registers of the microprocessor for external purposes, for example for display, during a software test. This does not change the user programs provided for the microcomputer and does not impair the operation of the microcomputer itself. For this purpose, certain machine cycles in which the information of the internal registers of the microprocessor exist on the data bus (DS) of the microcomputer, are determined with the aid of a machine cycle counter (MR). To request this operation, the machine cycle counter (MR) controls a separate register read program memory (RLSR), the information of which is used instead of that of the system memory (SSR) of the microcomputer. The microcomputers equipped with the test circuit are used in protection circuits, for example in railway protection engineering. <IMAGE>
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