Synchronous NAND Flash Interface for NOR-Compatible Random Access
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Solution Overview
Problem
Conventional NAND-type flash memory is unsuitable for applications requiring random byte/word access due to its asynchronous interface, while NOR-type flash memory offers random access but at lower density and higher cost, limiting substitution and compatibility between the two.
Innovation Solution
A synchronous NAND flash memory interface is developed, incorporating additional CLK and WAIT pins to enable compatibility with NOR-compatible microprocessors without requiring substantial glue logic, allowing for high-speed connections and increased read performance while maintaining backward compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If NAND-type flash memory uses an asynchronous interface, then it achieves high density and low cost, but it cannot support random byte/word access
Solution Approach 1:
The patent applies dynamics by making the interface mode configurable and switchable. The NAND flash memory device can dynamically operate in either asynchronous mode (for high density/cost efficiency) or synchronous mode (for random access capability). This is achieved through mode selection logic that allows the same hardware to adapt its interface behavior based on operational requirements, resolving the contradiction between density and access flexibility.
Solution Approach 2:
The patent changes the interface parameter from fixed asynchronous to configurable synchronous/asynchronous mode. By introducing clock signal synchronization and configurable timing parameters, the system can switch between operational modes to match different access patterns. This parameter change enables the memory to maintain high density while gaining random access capability when needed.
2Ease of operation
If NOR-type flash memory uses a synchronous interface, then it permits random access, but it has lower density and higher cost
Solution Approach 1:
The patent makes the NAND flash memory universal by enabling it to function with both NAND-compatible controllers (asynchronous mode) and NOR-compatible processors (synchronous mode). The dual-mode interface allows a single high-density NAND device to replace both traditional NAND and NOR flash memory roles, eliminating the need for separate low-density NOR devices and achieving cost savings while maintaining random access capability.
Solution Approach 2:
The interface dynamically adapts to different controller types. When connected to a NOR-compatible processor, the NAND memory operates in synchronous mode to provide random access. When connected to a NAND-compatible controller, it operates in asynchronous mode for optimal density. This dynamic adaptation resolves the contradiction between density and access type.
3Quantity of substance
If NAND flash memory is substituted for NOR flash memory, then cost and capacity improve, but interface compatibility is lost
Solution Approach 1:
The patent changes the interface parameters of NAND flash memory to include synchronous mode with clock signal support and configurable timing. This parameter change enables the NAND device to present a NOR-compatible interface when needed, allowing substitution in NOR applications while maintaining high density and low cost advantages. The mode selection logic ensures proper parameter configuration based on the connected controller type.
Solution Approach 2:
The patent creates a universal interface that can operate with both NAND and NOR controllers. By implementing dual-mode operation, the high-capacity NAND flash memory becomes compatible with existing NOR flash interfaces, enabling direct substitution in NOR applications without requiring interface changes in the host system. This universality resolves the compatibility issue while preserving capacity advantages.
4Productivity
If a synchronous interface is added to NAND flash memory, then read performance and flexibility improve, but device complexity increases
Solution Approach 1:
The patent implements dynamic mode switching that adds synchronous capability only when needed. The device includes mode selection logic that determines whether to operate in asynchronous or synchronous mode based on the connected controller. This dynamic approach provides high read performance when paired with NOR-compatible processors while maintaining simplicity when used with traditional NAND controllers, thus managing complexity effectively.
Solution Approach 2:
The patent adds synchronous interface capabilities to make NAND flash universal. By integrating both asynchronous and synchronous mode support within a single device, the patent achieves high read performance for synchronous operations while maintaining backward compatibility for asynchronous operations. This multi-functionality resolves the complexity issue by consolidating multiple interface modes into one unified device rather than requiring separate implementations.
Data Source
AI summary
A NAND-type flash memory device is described. In some embodiments, the memory device includes NAND-type flash memory cells, and a synchronous NAND interface. The synchronous NAND interface includes a standard NAND flash interface pin arrangement and a clock (CLK) pin. The synchronous NAND interface is configured to interface with a NOR-compatible memory interface.