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

Jan 21, 2025#FPGA73

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The document discusses the differences between the `if` and `case` statements in Verilog synthesis. The `if` statement has a hierarchy of logic conditions, with the innermost `if` having 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 among signals, although excessive nesting can lead to increased path delays and reduced speed. In contrast, `case` statements are ideal for mutually exclusive conditions without clear priority, resulting in faster circuits but larger area usage, synthesizing into an n-to-1 multiplexer.

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 operational 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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