Load Registers for Fuse Reload Latency Reduction
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Solution Overview
Problem
Accessing on-chip fuses during reset processes in electronic devices is time-consuming and unreliable due to high latency and limited access, affecting security and performance.
Innovation Solution
Implementing load registers to store fuse values, which can be accessed quickly and securely, reducing the need for frequent fuse access by checking a valid indicator before reading from the fuses, and reloading during hard resets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuse values are accessed directly during reset processes, then security boot flow can be executed, but latency is high and reset process is slow
Solution Approach 1:
The patent pre-loads fuse values into load registers before reset operations occur. The system maintains a cache of fuse data in fast-access memory (load registers) that can be quickly retrieved during reset and security boot operations, eliminating the need to access slow fuse hardware during time-critical operations.
Solution Approach 2:
The patent introduces load registers as an intermediary layer between the fuse hardware and the processing units. This intermediate cache stores fuse values and provides fast access during reset operations, while a fuse controller manages the interface between the slow fuse hardware and the fast load registers, mediating data transfer and access requests.
2Ease of operation
If fuse is accessed frequently during reset operations, then reset functionality is maintained, but fuse reliability deteriorates due to limited access cycles
Solution Approach 1:
The system pre-loads fuse values into load registers during normal operation or previous cycles, so that during reset operations the loaded values can be retrieved without accessing the fuse hardware again. This preliminary caching action preserves fuse integrity by minimizing the number of actual fuse access cycles.
Solution Approach 2:
The patent creates copies of fuse values and stores them in load registers. Instead of repeatedly accessing the original fuse hardware, the system uses these copied values stored in fast memory, which can be read unlimited times without degrading the original fuse. This copying mechanism maintains reset functionality while protecting fuse reliability.
3Speed
If load registers are implemented to cache fuse values, then access speed improves, but device complexity increases
Solution Approach 1:
The load registers and fuse controller are designed to serve multiple functions: they cache fuse values for fast access during reset operations, maintain security boot flow, and manage interface between fuse hardware and processing units. This multi-functionality justifies the added complexity by providing comprehensive benefits across multiple system operations.
Data Source
AI summary
A new approach is proposed that contemplates systems and methods to support post reset fuse reload for latency reduction. First, values of fuses are read once and stored into one or more load registers on an electronic device, wherein the load registers are protected. Once the values of the fuse are loaded into the load registers, a valid indicator of the load registers is set indicating that the values have been successfully loaded into the load registers. When other components of the electronic device need to access these values, the other components will check the load registers first. If it is determined that the valid indicator of the load registers is set, the stored values are read from the load registers instead of from the fuses. If the valid indicator of the load registers is not set, the values are loaded again from the fuses into the load registers.