Serial Flash XIP Caching for Embedded Processor Speed
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Solution Overview
Problem
Embedded processor systems face challenges in increasing memory size due to limited pin count, making it difficult to implement external serial flash memory access efficiently, as direct access to external flash memory is slow and increases processing overhead.
Innovation Solution
A configurable cache memory module is introduced between the processor and external serial flash memory, allowing the processor to access external serial flash memory as if it were main memory, with the cache module determining whether data is stored in the cache or the flash memory and managing communication via a serial interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If direct access to external serial flash memory is implemented, then memory size can be increased, but access speed decreases and processing overhead increases
Solution Approach 1:
A cache memory module is introduced as an intermediary between the processor and external serial flash memory. The cache memory stores frequently accessed code and data, allowing the processor to read from fast local memory rather than slow external flash memory for common operations. This mediator resolves the contradiction by providing both large memory capacity (through external flash) and fast access (through local cache).
Solution Approach 2:
The memory system is segmented into two distinct parts: a small, fast local cache memory for frequently accessed data, and a large, slow external serial flash memory for storage capacity. This segmentation allows each component to optimize for its specific function, with the cache handling speed-critical operations and flash providing bulk storage, thereby resolving the speed-capacity tradeoff.
2Quantity of substance
If external serial flash memory is accessed directly, then memory capacity is increased, but processing overhead increases
Solution Approach 1:
The cache memory pre-loads frequently accessed code and data into its local storage before they are needed by the processor. This preliminary action eliminates the need for the processor to repeatedly access the external flash memory, thereby reducing processing overhead and improving productivity while maintaining large memory capacity.
3Speed
If cache memory is introduced between processor and flash memory, then access speed improves, but device complexity increases
Solution Approach 1:
The cache memory serves as a simple intermediary component that sits between the processor and external flash memory. It provides basic caching functionality with standard read/write operations, managing the complexity of coordinating between different memory systems while improving access speed. The intermediary handles the complexity of data translation and access routing automatically.
Data Source
AI summary
A system including a processor, a memory controller, and a flash memory module. The processor is configured to generate a request to retrieve information corresponding to an address. The memory controller module includes a cache memory configured to store information, and a cache control logic module configured to determine whether the cache memory stores the information corresponding to the address, if the cache memory stores the information corresponding to the address, retrieve the information from the cache memory and provide the information to the processor, and if the cache memory does not store the information corresponding to the address, generate a flash memory read request based on the address. The flash memory module is configured to, in response to receiving the flash memory read request, provide the information corresponding to the address to the memory controller module.