Start-up clear circuit

Suppose we want to initialize all flip-flops to an initial state but do not want to use the initial condition of 0 or 1. The circuit below clears the flip-flop at the beginning of the simulation  

The Gate-level Simulation Options should be specified as X as shown below  

The Transient Analysis setup is the same as in the example without the start-up clear circuit  

We see that the flip-flop is initialized to an initial state of zero. 

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Always preset or clear all flip-flops before running a simulation. Use the digital setup dialog box or a start-up clear circuit to set the initial state of the flip-flops. 

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