[Solved] Using Logicworks Purpose Exercise Create Finite State Machine Fsm Detect Certain Eight Dig Q37236189
Using LogicWorks
The purpose of this exercise is to create Finite State Machine(FSM) which can detect a
certain eight digit binary sequence in a continuous serialbinary input stream. When the
correct sequence is detected, the single output signal should bea logical true value, in all
other cases it should be a logical false. This exercise isdesigned to allow a gradual
transition from strictly combinational circuits to a simplesequential circuit. Note that this
lab assignment is a group assignment with each group having nomore than 2 students.
Problem Statement: The “Gottcha Anti-Theft” Machine
There are many anti-theft devices on the market that attempt tofoil a would-be robber from
starting your car and driving off with it. One popular item hasa keypad like a touch-tone
telephone. In order to start your car, you must key in a secretfour digit decimal code, such
as ‘3719’. It only “remembers” the most recent four digits youhave keyed in. Thus the
sequence ‘3723719’ will let you start your car.
For simplicity here we use a code based on a sequence of eightbits, and use two push
buttons to enter a sequence serially. Each press of a buttonenters the corresponding digit.
Figure 1. The Gottcha machine in action.
As you key in the bits in sequence, the device outputs E = 0until the most recent eight bits
agree with a built-in secret code byte. Then E switches to1.
The shut-off gottcha: If 16 bits are toggled in without thesecret code being observed, the
system shuts off and won’t accept any more bits. Add a resetbutton to the system that
presumably only the owner could control: when RESET is pressedthe system is again
enabled and can accept bits.
Design and test (on LogicWorks) the miracle Gottcha machine. Dothis in two different
ways (thus designing and simulating two different circuits):
1) The Factory Preset Model: The specific secret byte preset atthe factory MUST be one
of your team members’ secret keys. For groups with singlemember, please use your
assigned secret key. You can find your secret key at the end ofthis document. All groups,
please explicitly explain which key is used for Factory PresetModel in your Readme file.
Your group will receive zero point if you don’t follow this keyuse policy specified above.
Do not use registers: solve for the finite state machine withthe fewest states and flip-flops
possible.
2) The User-Programmable Model: This machine allows the carowner to enter a secret
byte into a register. The user selects a byte using two hexkeyboards, and presses an
ENTERCODE pushbutton to store the code word. Now when themachine is used “in the
field”, the car owner enters a sequence using the samepushbutton arrangement as for the
previous machine. When the sequence so entered matches the codeword stored in the
register, E goes HIGH. As with the Factory Preset Model, if morethan 16 bits are entered
without the proper sequence being observed, the system shuts off(until RESET is pressed).
Some Hints:
1) These systems have no actual clock – the release of eitherpushbutton produces a
transition that is used to trigger the flip flops involved. Themain flip flops in the circuit
are triggered by this transition.
2) You might put the outputs of the two pushbuttons intoasynchronous inputs of a flip
flop, which therefore instantly stores the value (i.e. informs”which” pushbutton was
pressed) of the newest input bit. The output of this flip flopisthen used as the actual “input”
value.
3) Use a shift register in part 2 to store the most recentlyreceived bits. Compare the shift
register output to the programmed code word. (So part 2 is verysimple.)
Expert Answer
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