Abstract: A security subsystem controls the data transfer rights among components of a secured system via a common bus. The security subsystem includes a secure block that is coupled to an access controller, preferably via a hard-wired connection to the controller. This secure block exclusively controls the access rights among components, and can effectively isolate security functions and data from the main processor. Because the security is provided via access control to components or subsets of components via a common bus, an efficient and effective integration of the security subsystem within the secured system can be achieved.

Abstract: 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.

Abstract: A security subsystem controls the data transfer rights among components of a secured system via a common bus. The security subsystem includes a secure block that is coupled to an access controller, preferably via a hard-wired connection to the controller. This secure block exclusively controls the access rights among components, and can effectively isolate security functions and data from the main processor. Because the security is provided via access control to components or subsets of components via a common bus, an efficient and effective integration of the security subsystem within the secured system can be achieved.

Abstract: 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.

Abstract: The present invention provides a random sequence generator for generating an output signal having random values. The generator comprises a plurality of cells inter-connected to one another such that each cell receives, as an input, an output from each cell connected thereto and generates a cell output based on a current value of the cell output and each cell output received. The plurality of cells include k subsets, each subset including n cells. A pre-selected cell from each of the k subsets generates an output and the output of the k pre-selected cells is provided as the output signal of the generator. In a specific embodiment, each of the cells is a linear cellular automaton, with k being an instruction width and k*n being an instruction length. The invention is particularly suitable for internal self-testing of a microcontroller in a smart card. This eliminates the need for external test contacts and thus prevents potential break-ins through the external contacts.

Abstract: 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.

Abstract: 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.

Abstract: A filter circuit for separating video and audio signals has an extra resistive element added. This forms a bridge circuit that greatly increases the attenuation of the audio signal in the video channel.