Flash Memory Devices with Embedded DRAM for Firmware Updates
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Solution Overview
Problem
Flash memory devices face limitations in flexibility and turnaround time for updating firmware due to the use of ROM, CAM, and SRAM, which are inflexible and costly, especially when SRAM is used.
Innovation Solution
Incorporating embedded DRAM memory cells that are post-silicon programmable and cost-effective, replacing the majority of instruction ROM, CAM, and SRAM for storing firmware instructions, with a small portion of ROM retained for limited operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ROM, CAM, and SRAM are used to store firmware instructions, then the firmware can be stored and executed, but the flexibility and turnaround time for updating firmware are limited and costly
Solution Approach 1:
The patent changes the fundamental parameter of memory volatility from non-volatile (ROM) or static volatile (SRAM) to dynamic volatile (DRAM), enabling post-silicon programmability. This parameter change allows firmware to be updated after manufacturing by loading instructions into DRAM from external sources, providing both flexibility and reduced turnaround time compared to traditional ROM/SRAM architectures
Solution Approach 2:
The patent introduces dynamic reconfigurability by replacing static firmware storage (ROM) with dynamic memory (DRAM) that can be programmed after silicon fabrication. This allows the firmware to be dynamically updated and modified in the field, enabling rapid response to bugs, security issues, or feature updates without requiring new hardware manufacturing
2Speed
If SRAM is used to store firmware instructions, then fast access is achieved, but the cost increases significantly
Solution Approach 1:
The patent replaces expensive SRAM with cheaper DRAM technology. While DRAM requires periodic refresh operations, it offers significantly lower manufacturing costs and density advantages. The patent accepts the temporary nature of DRAM storage (requiring refresh) in exchange for reduced cost and improved manufacturing ease, while maintaining sufficient access speed for firmware execution
3Stability of the object's composition
If ROM is used to store firmware instructions, then non-volatile storage is achieved, but the ability to update firmware is limited
Solution Approach 1:
The patent segments the firmware storage function into two parts: non-volatile storage in flash memory for persistent firmware images, and volatile DRAM for active execution and post-silicon programming. This segmentation allows the system to maintain non-volatile storage capabilities while gaining the ability to update firmware dynamically by loading new images from flash into DRAM
Solution Approach 2:
The patent introduces DRAM as an intermediary between non-volatile flash storage and the CPU. This intermediary layer provides post-silicon programmability by allowing firmware to be loaded and updated in DRAM from flash or external sources, while maintaining the stability and non-volatile characteristics of flash storage for persistent firmware images
Data Source
AI summary
One example of a memory device includes an array of flash memory cells, an array of Dynamic Random Access Memory (DRAM) memory cells, and a controller. The controller is configured to execute first instructions stored in the array of DRAM memory cells to access the array of flash memory cells.