Designing Dual-Priority Encoder Using LabView

Paluru Sunitha and Naga Sunil Manohar Bole

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Step 29. Press Ctrl+b keys to remove broken wires and press Ctrl+u keys to clean up the diagram on the Block Diagram as shown in Fig. 3.

Step 30. Change the case to False condition in main Case Structure and connect all the Tunnels on right side of Case Structure to False (F) constant. Then all the Tunnels will be closed as shown in Fig. 4.

Step 31. Return to Front Panel. Save the VI and press the Run Continuously button to check for the operation of dual-priority encoder. Give different inputs and check the outputs for identifying the first-highest and second-highest priority request.

Checking the output
Fig. 5 shows the result for dual-priority encoder operations for first-highest and second-highest priority requests when the inputs I7, I5, I3 and I0 are asserted. Here, I7 has the highest priority, after that the next-highest priority will be given to I5. Hence, all the output LEDs A2, A1 and A0 glow, which is equivalent to 111 (also a binary representation of 7) in the highest-priority box. In the second-highest-priority box, B2 and B0 are on and B1 is off, which is equivalent to 101 (also a binary representation of 5). The output LEDs both AVALID and BVALID are asserted, because more than one input is asserted.

Fig. 6 shows the result when only one input I2 is asserted. Here, output LEDs A2, A1 and A0 show the highest-priority request 2 as 010 (binary representation of 2) and the output LEDs B2, B1 and B0 are turned off. The output LED AVALID only is asserted, because we asserted only single input and there is no second-highest-priority request. Here, note that the circuit will be on only when the enable input (En’) is in off condition, because it is an active low enable input.

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The authors Paluru Sunitha and Naga Sunil Manohar Bole were third-year B.Tech (electronics and communication) students from Maharaj Vijayaram Gajapathi Raj College of Engineering, Vizianagaram when they sent this project, under the guidance of Associate Professor M. Satyanarayana, last year

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