Volatile Non-Volatile Memory Cell Initialization
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Solution Overview
Problem
Volatile memory devices, such as SRAM, lose their initial state when power is lost, and existing nonvolatile memory devices require costly and complex mask changes for design modifications, making it difficult to set and retain initial states efficiently during manufacturing.
Innovation Solution
The integration of a non-volatile portion within a memory cell to define pre-coded information, allowing for an initialization sequence to set and retain the initial state of a volatile portion, even when power is lost, using a programmable mask to reduce manufacturing costs and enable design changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a volatile memory device (e.g., SRAM) is used, then fast access speed and low power consumption during operation are achieved, but the initial state is lost when power is lost
Solution Approach 1:
The memory device is segmented into a volatile memory portion (for fast access) and a non-volatile memory portion (for retaining initial state). The volatile portion contains SRAM cells for rapid data access, while the non-volatile portion stores the initial state information. This segmentation allows the device to simultaneously achieve fast access speed during operation and retention of initial state after power loss.
Solution Approach 2:
The initial state is predetermined and stored in the non-volatile memory portion during manufacturing. When power is applied to the device, an initialization sequence automatically copies this pre-stored initial state to the volatile memory portion, ensuring the device starts with a known state without requiring external initialization operations.
2Reliability
If a non-volatile memory device (e.g., ROM) is used, then the initial state is retained after power loss, but costly and complex mask changes are required for design modifications
Solution Approach 1:
The memory device is designed to perform multiple functions: it operates as a volatile memory during normal operation for fast access, and as a non-volatile memory for retaining initial state. Additionally, the non-volatile portion can be programmed after manufacturing to store different initial states, providing versatility without requiring costly mask changes for design modifications.
Solution Approach 2:
The device transitions between different operational modes: during normal operation, it functions as fast volatile memory; after power loss, it initializes from the non-volatile portion; and it can be dynamically reprogrammed to change the initial state stored in the non-volatile portion, providing adaptability without manufacturing changes.
3Ease of manufacture
If the state of volatile memory is set after manufacturing, then the initial state can be defined, but the state is lost when power is lost
Solution Approach 1:
The non-volatile memory portion acts as an intermediary between the manufacturing process and the volatile memory operation. During manufacturing, the initial state is stored in the non-volatile portion. When power is applied, this intermediary automatically transfers the stored state to the volatile memory portion, ensuring both ease of manufacturing and retention of state.
Data Source
AI summary
A memory device comprising memory cells having volatile and non-volatile memory portions. The volatile memory portion of each cell includes circuitry for performing RAM functions while the non-volatile memory portion comprises circuitry defining pre-coded data. The memory device comprises a mechanism to operate an initialization sequence, which sets the initial state of the volatile memory portion of each memory cell to the pre-coded data defined in the associated non-volatile memory portion. The initialization sequence allows the initial state of each memory cell's volatile portion to be re-established after power has been applied to the memory device.