Chapter D Finite State Machines

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Question 7. Design an FSM controller for a safe lock. The lock should only open ifthe sequence RLLRR is received. Any other sequence should sound the alarm.ACTIVITIES 2Question 8. Load up the FSM Robot Simulator from HERE. Unzip the folder anddrop on your desktop. Now double click on the executable jar file *.jar" Note this isexperimental software currently under development for you. The version we are usingtoday is still a little rough. Fingers crossed.1.1 Make a FSM Table so that the robot will move forwards until its left bumper hits.Then it should move backwards for ever. Load RWorld1.1.2 Make a FSM Table so that the robot moves forwards until it hits the obstaclewhen it should turn right (clockwise) until its bumper is clear, when it should gostraight on.1.3 Single step the machine (brown man). Confirm your expectations. What happenswhen the robot hits the wall? Why does it not respond to the wall?Question 9. Load up "Controller 1" and "World4". The FSM was designed to allowthe robot to move in and then out of the channel. But there's a mistake and it doesn'twork well.9.1 Observe the behavior of the robot.9.2 Look at the FSM table and work out what is going on9.3 There is an error in the table. Find it and correct it. Demonstrate the correct codeto your tutor or friend.Question 10. Let's say we want to get the robot to go around the edge of a squareblock. We could use its left feeler to probe for the edge of the block, and use this leftfeeler as the robot moves around the block. Consider the left feeler touching theblock. How should we instruct the robot to move? Consider the left feeler nottouching the block - the robot is moving away from the block. How should we instructthe robot to move?Drawa state diagram for this problem. Fill out a FSM table and try out your solutionusing "World2" One correct solution is found in "Controller2.txt"ACTIVITIES 3 Digital Electronic Finite State Machine
The following activities lead you through the procedure to construct a FSM in digitalelectronic hardware.Question 1 First let’s attack a paper-based question to review the principles of a FSMconstructed from a memory chip and a latch chip. Then we shall implement thisdesign using MultiMedia Logic simulator.The sketch below shows a memory chip with 16 cells (0 to F), each cell contains 4bits of data. Two of these bits are used as outputs, the other two bits are recycled toprovide the address information of the next state. The four bit emerge from thememory chip at its bottom and pass into the 4-bit data register shown there. The twoaddress bits emerging from this data register are complemented by a further two inputbits a and b which together form a 4-bit address which is shown on the left.[modify diagram to make order of these address bits explicit]1.1 Complete the contents of the memory so that when input b=0, then the output datawill repetitively cycle between the values 0 -> 1 ->2 ->3 ->0 and so on. Take inputa=0;1.2 Modify your table so that in addition to the above output, the FSM generates thereverse sequence 3 -> 2 -> 1 -> 0 -> 3, etc when input b=1. Take input a=0;1.3 Explain how you would need to modify the above circuit to be able to drive asystem of traffic lights through the states “red”, “red and amber”, “green”,“amber” and back to “red”.1. Configure the above ROM with latch so that when input b is 0 then the outputscycle through the sequence 0 -> 1 -> 2 -> 3 -> 0 -> …, and when input b I 1,the outputs cycle through 3 -> 2 -> 1 -> 0 -> 3 -> … Input a is set always to 0.2. Explain how you would need to modify the above system to be able to drive asystem of traffic lights through the states “red”, “red and amber”, “green”,“green”, “amber”, “red”.3. Explain how you would modify your design so that if a pedestrian pressed abutton (say “a”) then the lights would go to “amber” then “red”.Question 2. Here is a Multimedia Logic Circuit which implements the Finite StateMachine presented above. The memory cell, top centre is the ROM, and the tworectangular “flipflops” make up the latch. The top two LEDs are the data outputfrom the system. The additional OR-Gates have been included simply to reset themachine to a distinct starting state.N.B. When you start each simulation, set the “Reset” switch to “1”, then press the“Clock” switch, and the reset the Reset switch (!) to “0”. This will reset thecircuit.
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Chapter D Finite State Machines

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