DSP Block Cascade Input Design for Reduced FPGA Pin Count
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Solution Overview
Problem
In modern field programmable gate array (FPGA) architectures, digital signal processing (DSP) blocks face high pin counts due to direct connections and lack of efficient routing, leading to increased routing congestion, especially in fine-grained architectures where dedicated switch blocks are absent.
Innovation Solution
The design introduces a DSP block with reduced pin counts by utilizing sign-extension sub-blocks for connecting reduced-width inputs to full-width adders, implementing a cascade path for input concatenation, and a shared input for shift-argument, which reduces the pin requirements and allows for flexible full-width access without increasing the pin count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If DSP blocks use direct connections with full-width input ports, then routing flexibility is improved, but pin count increases and routing congestion worsens
Solution Approach 1:
The input interface is segmented into a reduced-width port (e.g., 18 bits) and a shift-argument port (e.g., 4 bits). This segmentation allows the DSP block to accept full-width data (up to 64 bits) by combining the reduced-width input with shift operations, thereby reducing pin count while maintaining routing flexibility and full-width processing capability.
2Measurement precision
If DSP blocks use full-width input ports for direct connections, then processing precision is improved, but routing congestion increases
Solution Approach 1:
The patent introduces a time dimension through shift operations. Instead of requiring all full-width inputs to be available simultaneously on separate pins, the system uses a reduced-width port combined with shift-argument control to construct full-width values over time. This dimensional transformation reduces spatial routing requirements while preserving processing precision.
3Quantity of substance
If DSP blocks use reduced-width input ports, then pin count is reduced, but connection complexity increases
Solution Approach 1:
The DSP block performs self-service by internally generating the full-width data width through shift operations. The reduced-width input port combined with the shift-argument register allows the block to construct full-width values using its own internal resources (shifters, multiplexers), eliminating the need for external full-width routing infrastructure and reducing connection complexity.
Data Source
AI summary
A digital signal processing block has a first input port, a second input port, a third input port, a cascade input port and an output port. The DSP block may have a cascade output port. The DSP block may have a multiplexer that has selectable output, to the cascade output port, of concatenated inputs from the first input port, the second input port and the third input port. The DSP block may be connectable to another DSP block via a cascade path. The DSP block may have a variable shifter. The DSP block may have a full-width adder and reduced-width input ports.