Serial Memory Bus Transactions With Encoded Length Metadata
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Solution Overview
Problem
Conventional memory device transactions lack the ability to specify data transfer size before the transfer begins, which hinders the implementation of security features such as authentication tags, and are not compatible with execution-in-place designs.
Innovation Solution
A method where a memory device receives encoded data length (LEN) values with command and address values, allowing for variable data transfer sizes determined by serial clock cycles, and includes metadata for authentication and encryption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional SPI transactions use fixed data length or host de-assertion of chip select signal to determine transfer size, then the protocol is simple and easy to implement, but the ability to specify data transfer size before transfer begins is lost, hindering security features implementation
Solution Approach 1:
The patent applies preliminary action by encoding the data length (LEN) value in the command sequence before the actual data transfer begins. The host device transmits the LEN value along with the command and address, allowing the memory device to know the exact data transfer size in advance. This enables security features like authentication tags to be properly implemented since the data boundaries are predetermined, while maintaining protocol simplicity through the existing SPI command structure.
2Reliability
If shadow memory is used for security authentication, then code can be authenticated before execution, but execution-in-place designs are not compatible since only volatile memory code is authenticated
Solution Approach 1:
The patent applies universality by creating a protocol that works for both shadow memory authentication and execution-in-place designs. By specifying the data length before transfer, the same SPI protocol can be used to authenticate code in shadow memory or to transfer authentication tags with code executed directly from nonvolatile memory. This multi-functional approach allows the protocol to support multiple security architectures without requiring separate mechanisms.
3Adaptability or versatility
If variable data transfer sizes are enabled with encoded LEN values, then security features like authentication tags and execution-in-place operations are supported, but the command sequence complexity increases
Solution Approach 1:
The patent applies merging by combining the data length specification into the existing command and address sequence rather than creating a separate mechanism. The LEN value is encoded and transmitted as part of the standard SPI command sequence, merging the length specification function with the existing command structure. This reduces overall system complexity by reusing established protocol elements rather than adding separate control mechanisms.
Data Source
AI summary
A method can include receiving, at a serial input/output (IO) of a memory device, at least command values, address values and metadata that includes an encoded length value in synchronism with a serial clock. From at least the command, address and encoded length values, a memory access operation, a memory array location, and one of a plurality of different data length values (LEN) corresponding to the memory access operation can be determined. At least data having a length corresponding to the one of the plurality of different LEN can be transferred at the serial IO in synchronism with the serial clock during execution of the memory access operation. Corresponding devices and systems are also disclosed.