State Transition Table Analysis Now how the State Transition Table was generated from the State Graph. For let’s look at each state, there must be 4 sets of inputs that cause a transition. So with 4 possible states, there are actually 8 sets of inputs that must be checked on each clock signal to determine if the state is held or if a transition to the next state will take place. In the first line of the transition table (S0), the gate is closed. In the second line of the transition table (S0), the Open Switch Pushbutton is pressed by the operator. Without looking at the notes on the previous page, begin on LINE 2 and see if you can accurately predict the NEXT STATE and the outputs as you move down each consecutive line. Below each line in the transition table is a box where you can describe (in your own words) what is happening at the tollbooth. The first few descriptions have been given as examples to get you started. After you have worked through the table you can go back and put in the “Don’t Care” comments. Note: This handout is meant to be a tool that helps you understand the tollbooth state machine design. It is for your use only. You should be documenting all of your work for final evaluation in your engineering notebook or project portfolio. Tollbooth State Transition Table Analysis Operator Limit Switches NEXT STATE* Outputs PRESENT STATE Pushbuttons Open Close Open Close Motor Motor Gate Gate State Qa Qb State Qa* Qb* Switch Switch Limit Limit Open Close Open Closed S0 0 0 0 0 S0 0 0 1 The gate is closed with no inputs from the operator. S0 0 0 1 0 S1 0 1 0 1 The operator has pressed the pushbutton the gate is still closed. should be the next state. “OPEN SWITCH” but “MOTOR OPEN” S1 0 1 0 S1 0 1 1 0 0 The gate is opening but has not reached the the should be the next state. “OPEN LIMIT”. Hitting “OPEN LIMIT” S1 0 1 1 S2 1 0 1 0 0 The gate has reached the but the is still with motor off should be the next “OPEN LIMIT” “MOTOR OPEN” on. “GATE OPEN” state. S2 1 0
State Transition Table Analysis Now let’s look at how the State Transition Table was generated from the State Graph. For each state, there must be 4 sets of inputs that cause a transition. So with 4 possible states, there are actually 8 sets of inputs that must be checked on each clock signal to determine if the state is held or if a transition to the next state will take place. In the first line of the transition table (S0), the gate is closed. In the second line of the transition table (S0), the Open Switch Pushbutton is pressed by the operator. Without looking at the notes on the previous page, begin on LINE 2 and see if you can accurately predict the NEXT STATE and the outputs as you move down each consecutive line. Below each line in the transition table is a box where you can describe (in your own words) what is happening at the tollbooth. The first few descriptions have been given as examples to get you started. After you have worked through the table you can go back and put in the “Don’t Care” comments. Note: This handout is meant to be a tool that helps you understand the tollbooth state machine design. It is for your use only. You should be documenting all of your work for final evaluation in your engineering notebook or project portfolio. Tollbooth State Transition Table Analysis PRESENT STATE Operator Pushbuttons Limit Switches NEXT STATE* Outputs State Qa Qb Open Switch Close Switch Open Limit Close Limit State Qa* Qb* Motor Open Motor Close Gate Open Gate Closed S0 0 0 0 0 S0 0 0 1 The gate is closed with no inputs from the operator. S0 0 0 1 0 S1 0 1 0 1 The operator has pressed the pushbutton “OPEN SWITCH” but the gate is still closed. “MOTOR OPEN” should be the next state. S1 0 1 0 S1 0 1 1 0 0 The gate is opening but has not reached the “OPEN LIMIT”. Hitting the “OPEN LIMIT” should be the next state. S1 0 1 1 S2 1 0 1 0 0 The gate has reached the “OPEN LIMIT” but the “MOTOR OPEN” is still on. “GATE OPEN” with motor off should be the next state. S2 1 0
4.1.3.P%20StateMachines_Tollbooth_VEX_DMS.docx