| 摘要 |
Chip cards comprising a microprocessor and a memory are used for various applications. It is also desirable that such chip cards can be used for different applications. This requires a strict and reliable separation of the various user programs so that mutual accessing is not possible. This is achieved notably by subdivision into a system mode, in which all access rights are free, and a user mode which is adjusted by way of a given bit in the program status word. This mode bit controls inter alia a separation in the bus for the special function registers so that given registers are not accessible in the user mode. These registers may contain information enabling the access to given memory sections only, so that this access cannot be modified in the user mode. Furthermore, each memory word may contain respective test information which is individually associated with a user program and is compared with the appropriate test information upon reading out, the information read out not being internally transported further in the case of lack of correspondence.
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