Microprocessor-controlled apparatus including an antitheft protection means which can be disabled.

摘要

Microprocessor-controlled apparatus, for example, a car radio whose microprocessor (5) is one-time programmable by the manufacturer of the apparatus. An external non-volatile memory (7) comprises a security variable (VAR) indicating whether the protection means is operational. In addition to a security code (SC), an arbitrary code series (KEY) of, for example, 20 bits is stored in the internal memory (51) of the microprocessor (5). Unauthorized disabling of the protection means by external interrogation of the non-volatile memory (7) is only possible by assigning a value which corresponds to the code series (KEY) to the security variable. However, the code series (KEY) is inaccessible and can only be traced with great difficulty by means of trial and error methods. <IMAGE>