Shadow RAM Buffering for Serial NAND Flash XIP
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Solution Overview
Problem
NAND Flash memory lacks direct random access and Execute in Place (XiP) capability, resulting in slower code execution and higher error rates due to bad bits, which hinder efficient data reading and processing.
Innovation Solution
The method involves mirroring data from NAND Flash memory to a shadow RAM upon device power-on, enabling random access and error correction, and using a serial peripheral interface (SPI) for data transmission, allowing for efficient data transfer and execution in XiP mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If NAND flash memory is used, then memory density and write speed are improved, but read speed and random access capability deteriorate
Solution Approach 1:
The patent creates a copy of the NAND flash memory interface in the form of a shadow RAM buffer. This shadow RAM stores copies of frequently accessed data and instructions, allowing the host processor to read from the fast shadow RAM instead of the slower NAND flash memory, thereby resolving the contradiction between high memory density and fast read speed.
Solution Approach 2:
The shadow RAM acts as an intermediary between the NAND flash memory and the host processor. It buffers data transfers and provides a fast access path for read operations, while the NAND flash memory continues to provide high-density storage. This intermediary layer eliminates the direct performance bottleneck.
2Quantity of substance
If NAND flash memory is used, then memory density is improved, but random access capability and execute in place capability deteriorate
Solution Approach 1:
By copying data from NAND flash memory into shadow RAM, the system enables random access to frequently used instructions and data. The shadow RAM maintains the same address space mapping as the original NAND flash, providing transparent random access capability while using faster memory technology.
Solution Approach 2:
The patent segments the memory access function into two parts: NAND flash memory handles dense storage and less frequently accessed data, while shadow RAM handles frequently accessed data and instructions requiring random access. This segmentation allows each memory type to operate in its optimal performance regime.
3Quantity of substance
If data is read directly from NAND flash memory, then storage capability is improved, but error rates increase due to bad bits
Solution Approach 1:
The shadow RAM serves as an intermediary that buffers data from NAND flash memory before it reaches the host processor. This intermediate buffer allows for better error detection and correction mechanisms to be implemented, as errors can be detected during the transfer to or from the shadow RAM rather than directly from the storage medium.
Solution Approach 2:
The system performs preliminary data transfer to shadow RAM during system initialization or idle periods, allowing error detection and correction to be performed in advance before the data is needed for execution. This preliminary action enables the system to handle bad bits proactively rather than reactively.
4Quantity of substance
If code execution is performed in NAND flash memory, then storage capability is improved, but execution speed deteriorates
Solution Approach 1:
The patent copies instructions and data from NAND flash memory into shadow RAM, enabling the host processor to execute code from the fast shadow RAM memory rather than directly from the slow NAND flash memory. This copying operation significantly improves execution speed while maintaining the ability to store large amounts of data in the NAND flash memory.
Solution Approach 2:
The system performs preliminary loading of frequently executed code and data into shadow RAM during system boot or idle periods. This preliminary action ensures that when code execution is needed, the processor can access instructions from the fast shadow RAM buffer, dramatically improving execution speed without compromising the storage capability of the NAND flash memory.
Data Source
AI summary
Based on power on of an electronic device, a location of first data in a NAND flash memory of an electronic device is determined. The first data is transmitted to a shadow RAM of the electronic device, outputting the first data is output from the shadow RAM to a host device of the electronic device through a serial peripheral interface (SPI) when accessing the location of the first data in the NAND Flash memory.