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l11_ece15a_6

# l11_ece15a_6 - Combinational Logic Word Problems 1...

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1 ECE 15A Fundamentals of Logic Design Lecture 11 Malgorzata Marek-Sadowska Electrical and Computer Engineering Department UCSB 2 Combinational Logic Word Problems 1. Understand the problem what is the circuit supposed to do? write down inputs (data, control) and outputs draw block diagram or other picture 2. Formulate the problem in terms of a truth table or other suitable design representation 3. Follow implementation procedure K-maps, CAD tools (espresso, sis) 3 Process Line Control Problem Statement of the Problem: Rods of varying length (+/-10%) travel on conveyor belt, mechanical arm pushes rods within spec (+/-5%) to one side Second arm pushes rods too long to other side Rods too short stay on belt 3 light barriers (light source + photocell) as sensors Design combinational logic to activate the arms 4 Process Line Control Problem Where to place the light sensors A, B, and C to distinguish among the three cases? Understanding the Problem Inputs are three sensors, outputs are two arm control signals Assume sensor reads "1" when tripped, "0" otherwise Call sensors A, B, C Spec + 5% +10% Too Long ROD Spec + 5% - 5% Within Spec ROD Spec - 5% - 10% Too Short ROD 5 Process Line Control Problem Assume that A detects the leading edge of the rod on the conveyor Assumptions •Rods are placed perpendicularly to the direction of belt’s motion. •Rods are pushed to one side of the belt. 6 Process Control Problem A to B distance place apart at specification - 5% A to C distance placed apart at specification +5% A B C Spectification - 5% Specification + 5% Too Long Too Short Within Spec

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