Combinational loop example

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A combinational loop is a unregistered feedback loop.  This source code has a combinational loop.




This Synopsys Design Compiler synthesis script checks the design for combinational loops, reporting detection of a timing loop for the design.


To eliminate the combinational loop, we can add a rising-edge-triggered register, as in this source code.




This Synopsys Design Compiler synthesis script checks the design for combinational loops, reporting no timing loops for the design.