An access control circuit for use with supervisory logic circuitry in a method of protecting software for embedded applications from unauthorized access

摘要

An access control circuit for controlling access to a protected memory area for use with supervisory logic circuitry in a method of protecting software for embedded applications from unauthorized access, wherein the software is loaded into the protected memory area and the access control circuit includes an address decoder having inputs to which higher address bits are applied and having an output which outputs an area signal when an address having the address bits is within a predetermined address range, and wherein the address decoder outputs a zero range signal when an address to an associated memory location within the address range protected memory area, which refers to protected address locations within the protected memory area, characterized in that the access control circuit comprises a monitoring logic circuit arrangement with a flip-flop which contains the null-range signal and logic gates, which combine the latched null-range signal from the output of the flip-flop with an area signal provided as a result of decoding a following address from the address decoder, thereby causing the flip-flop to output a status signal indicative of a Memory access into the protected memory area is representative of within the protected memory area.