Differences in the circuits synthesized from if statements and case statements in Verilog

Jan 21, 2025#FPGA310

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The document discusses the differences between the `if` and `case` statements in Verilog synthesis. It highlights that `if-else` statements have a priority hierarchy, where the innermost `if` has the highest priority, while `case` statements evaluate conditions in parallel. Each `if-else` structure synthesizes into a 2-to-1 multiplexer, making it suitable for scenarios with clear priority but potentially leading to increased path delays if overly nested. In contrast, `case` statements are ideal for logic conditions without clear priority, synthesizing into an n-to-1 multiplexer, which is faster but occupies more area.

The difference is that the logical judgment of if else has priority, with the innermost if having the highest priority, while the logical judgment of case is parallel. Each circuit synthesized from if else is a 2-to-1 multiplexer. This statement is used when there is a clear priority among signals, but too many nested if statements can lead to excessive path delays, reducing operating speed. Therefore, it is used when there are fewer conditions. The circuit area synthesized from if else is relatively small.
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The case statement is suitable for logical judgments without clear priorities, where these logical conditions are at the same priority level and mutually exclusive, such as implementing high-speed encoding and decoding; the case structure circuit is faster but occupies a larger area, synthesized as an n-to-1 mux circuit.
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