Bus Decoder with Integrated Security Filtering
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Solution Overview
Problem
Existing bus decoding systems face challenges in efficiently implementing security filtering without compromising the speed of bus transactions, as they often require separate modules on the master side or address filters on the slave side, which can steal time from the bus access paths.
Innovation Solution
A bus decoder that is operationally connectable to master and slave units, which receives an address from a master unit, maps it to a slave address, associates default access permissions, determines additional access permissions, and enables or rejects the master-slave connection based on these permissions, all while maintaining low overhead and parallel lookups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate security filtering modules are added to the master or slave side, then security filtering capability is improved, but bus access time increases
Solution Approach 1:
The patent combines the security filtering function with the bus decoder by integrating permission checking logic directly into the decoding process. The bus decoder now simultaneously performs address decoding and access permission verification, eliminating the need for separate security filtering modules that would otherwise add time to the bus access path.
Solution Approach 2:
The bus decoder is enhanced to perform multiple functions: traditional address decoding plus security filtering. By making the bus decoder a multi-functional component that handles both address translation and permission checking, the system avoids adding separate dedicated security modules that would increase bus access time.
2Reliability
If complex security filtering is implemented, then security control capability is improved, but device complexity increases
Solution Approach 1:
The patent implements preliminary action by pre-configuring access permission tables that store default permissions and additional permissions for different master units and address ranges. During bus operations, the decoder simply looks up pre-computed permission values rather than performing complex real-time security evaluations, thereby achieving sophisticated security control without proportionally increasing operational complexity.
Solution Approach 2:
The security filtering functionality is segmented into distinct permission tables: default access permissions table and additional access permissions table. This segmentation allows the complex security control logic to be organized into manageable, independent data structures that can be efficiently queried without overwhelming the decoder logic.
Data Source
AI summary
According to an aspect, there is provided a solution for providing an access to a slave unit. An address from a master unit trying to access a slave unit is received (400). The received address is mapped (402) to a slave address. Default access permissions are associated (404) to the master-slave connection. Additional access permissions associated with the master unit and the slave address are determined (406). The master-slave connection is enabled (408) if additional access permissions allow the master unit to access the slave, otherwise the connection is rejected.