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Unformatted text preview: c A.H.Dixon Laboratory Exercise 5 1 FEEDBACK LOOPS The purpose of this lab is to experiment with digital circuits that have feedback loops; that is, an output of the circuit also serves as an input to the same circuit. 1. On a new design page in DesignWorks (LogicWorks) construct the following circuit: keyboard 3 7 B F Q R S binary probe Figure 1: example caption Note: Only two outputs from the keyboard will be used, as you will only be “pushing” keys 0, 1, 2, and 3 on the keyboard. 2. In The “SImulation” pulldown menus select “Simulation Params...” and change the propagation delay for each NAND gate to 10 ns by entering that value in the field provided. 3. If you haven’t done so, label the inputs and output as indicated on the diagram. These labels should appear in the Timing Window. 4. Click on the “Zoom In” button (with icon ¡¿) so that the waveform scale is display in 10 ns intervals. 5. Begin a simulation of the circuit by first clicking on key “1’” of the keyboard. Using step-mode advance the timing by clicking the step-mode (“walking man”) button until the waveform diagram has advanced to 30ns. The initial value displayed on the binary probe before starting the simulation is not relevant. (It may be 0, 1, or X). It should eventually be 0....
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- Spring '08
- The Circuit, Input/output, Cybernetics