Crossbar Circuitry with Reused Data Paths for Scalable Routing
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Solution Overview
Problem
Existing crossbar circuit designs are complex, consume significant power, and lack scalability due to the large number of control lines required for routing control signals, which becomes impractical as the size of the crossbar increases, especially when handling multi-bit data and large numbers of inputs and outputs.
Innovation Solution
The design incorporates crossbar cells with storage circuitry and transmission circuitry at each intersection, where data input paths are connectable to destination paths based on programmable routing values, and control circuitry re-uses data output paths for programming, reducing the need for separate control lines and enabling flexible and efficient configuration and operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional MUX-based crossbar circuits are used to route data from any input to any output, then routing flexibility is achieved, but the circuit size and power consumption increase significantly
Solution Approach 1:
The patent extracts the routing control function from complex MUX-based structures and implements it through simple crossbar cells with storage elements at each intersection. Each cell independently stores a routing value (0 or 1) that controls whether data passes through, eliminating the need for hierarchical MUX arrangements and significantly reducing circuit area while maintaining routing flexibility.
Solution Approach 2:
The crossbar circuit is segmented into independent cells at each input-output intersection, where each cell contains its own storage element and transmission transistor. This segmentation allows each cell to operate independently and simplifies the overall circuit architecture compared to monolithic MUX-based designs, reducing total circuit area.
2Measurement precision
If traditional crossbar circuits use separate control lines for each crosspoint, then routing control is precise, but the number of control lines grows rapidly with size
Solution Approach 1:
The patent merges the control signal routing with the data path routing by using the same physical lines for both purposes. The storage elements are programmed during a configuration phase using these lines, and then they maintain their state during data transmission without requiring continuous control signals. This merging eliminates the need for separate control lines for each crosspoint, reducing overall circuit complexity.
Solution Approach 2:
The routing configuration is performed in advance during a programming phase before data transmission begins. Storage elements are programmed with routing values (0 or 1) that determine data paths, and once programmed, they maintain their state without requiring continuous control. This preliminary configuration eliminates the need for continuous control lines during data transmission.
3Adaptability or versatility
If crossbar circuits increase in size to accommodate more inputs and outputs, then routing capability improves, but layout complexity and power consumption increase
Solution Approach 1:
Each crossbar cell contains local storage elements and transistors that are identical in structure, creating a regular, repeating pattern throughout the circuit. This local uniformity simplifies layout design and manufacturing compared to non-uniform MUX-based structures, and the regular pattern scales predictably with circuit size without proportionally increasing layout complexity.
4Adaptability or versatility
If data paths are made longer to accommodate more outputs, then routing flexibility improves, but capacitance increases requiring larger drive transistors
Solution Approach 1:
The patent extracts the routing decision function from the data transmission path and places it in storage elements at each intersection. This allows data to be transmitted directly through simple transistors without requiring complex buffering or driver amplification along long paths, as the routing is predetermined by stored values rather than dynamically controlled through multiple stages.
Data Source
AI summary
Crossbar circuitry, and a method of operation of such crossbar circuitry, are provided. The crossbar circuitry has an array of data input paths and data output paths where the data output paths are transverse to the data input paths. At each intersection between a data input path and a data output path, a crossbar cell is provided that comprises a storage circuit programmable to store a routing value, and a transmission circuit. In a transmission mode of operation the transmission circuit is responsive to the routing value indicating that the data input path should be coupled to the data output path to detect the data input along the data input path, and to output an indication of that data on the data output path at the associated intersection. Control circuitry is used to issue control signals to the crossbar cells, and during a configuration mode of operation the control circuitry re-utilizes at least one of the data output paths to program the storage circuitry of one or more of the crossbar cells. Such a construction of crossbar circuitry provides a very regular design, with uniform delay across all paths, and which requires significantly less control lines than typical prior art crossbar designs. Such crossbar circuitry is readily scalable to form large crossbars.