7.4 Clocked Synchronous State-Machine Design>Theclockedsynchronous[ni(]'m nik]stateadj.记忆的，记忆术的，1. Cdtable corresponding帮助记忆的to the woracscription or specification, usingmnemonic names for the states.mber of states in2. (Optiona)a［ 'sainm nt]the state/outp n.分配,委派，任务，imization).(课外)作业bles and assign3. Choose astate-variable CmDinations to the named states.state assignment)4. Create a transition/output table.5. Choose a flip-flop type for the state memory
5. Choose a flip-flop type for the state memory. Return Next 7.4 Clocked Synchronous State-Machine Design 1. Construct a state/output table corresponding to the word description or specification, using mnemonic names for the states. ➢ The steps for designing a clocked synchronous state machine: [ni(:)’m nik] adj.记忆的, 记忆术的, 帮助记忆的 2. (Optional) Minimize the number of states in the state/output table(state minimization). 3. Choose a set of state variables and assign state-variable combinations to the named states. (state assignment) 4. Create a transition/output table. [ ’sainm nt] n.分配, 委派, 任务, (课外)作业
7.4ClockedSynchronous State-MachineDesign6, Construct an excitation table7. Derive excitation equations from theexcitation table.8. Derive output equations from the transition/output table.9. Draw a logic diagram.10. Check self-startup capability7.4.1 State-Machine Design ExampleProblem:Designaclocked synchronousstate machinewithtwoinputs,AandB,andasingleoutputzthat is 1 if:
Design a clocked synchronous state machine with two inputs, A and B, and a single output Z that is 1 if: 7.4 Clocked Synchronous State-Machine Design 6. Construct an excitation table . 7. Derive excitation equations from the excitation table. 8. Derive output equations from the transition/ output table. 9. Draw a logic diagram. 7.4. 1 State-Machine Design Example 10. Check self-startup capability. Problem: Return Back Next
7.4 Clocked Synchronous State-Machine Design(1)Ahadthesamevalueateachofthetwoprevious clock ticks,or(2)Bhasbeen 1since the last that the firstcondition was true.Otherwise,theoutputshouldbeOSolution:1. Construct State/Output TableFrom the word description, we know the outputof the state-machine depends only on the currentstate(what happened in previous clock period), soit's a Moore machine
From the word description, we know the output of the state-machine depends only on the current state(what happened in previous clock period), so it’s a Moore machine. 7.4 Clocked Synchronous State-Machine Design (1) A had the same value at each of the two previous clock ticks, or (2) B has been 1 since the last that the first condition was true. Otherwise, the output should be 0 1. Construct State/Output Table Solution: Return Back Next
7.4Clocked Synchronous State-Machine DesignHow many states we need at least for theoriental word description?So: Initial state.AB00110110zsS,: Got A=0 on theSn+!Sn+1Sn+1Sn+1previous tick, A+0 onSoS1S2S2S1the tick before, andS1S3S3S2S2B+1 at some timeS2S1S1S4S4since the previous pairof equal A inputs.S3S3S3S4S2S4S4S4S,: Got A=1 on theS1S3previous tick, A+1 onS: Got two equal A(=O) inputs, orthe tick before, andB=1 after a pair of equal A inputsB+1 at some timeand A=0 last.sincethepreviouspairS4: Got two equal A(=1) inputs, orof equal A inputs.B=1 after a pair of equal A inputs,and A=1 last
S2 : Got A=1 on the previous tick, A≠1 on the tick before, and B≠1 at some time since the previous pair of equal A inputs. S1 : Got A=0 on the previous tick, A≠0 on the tick before, and B≠1 at some time since the previous pair of equal A inputs. We can construct a state/output table template given in previous section. 7.4 Clocked Synchronous State-Machine Design 0 1 S AB 0 0 1 1 1 0 Z S n+1 S n+1 S n+1 S n+1 S0 : Initial state. S3 : Got two equal A(=0) inputs, or B=1 after a pair of equal A inputs, and A=0 last. How many states we need at least for the oriental word description? S1 S1 S2 S2 S3 S3 S2 S2 S1 S1 S4 S4 S3 S3 S4 S2 S1 S0 S1 S2 S3 S4 S3 S4 S4 Return Back Next S4 : Got two equal A(=1) inputs, or B=1 after a pair of equal A inputs, and A=1 last
7.4 Clocked Synchronous State-Machine Design2.State MinimizationThe state/output table constructed in previouspage is "minimal". If the other tables with morestates(e.g. P368 Figure 7-51), we need minimizethe number of states in such tables- A pair of equivalent states can be replaced by a singlestate. Two state S1 and S2 are equivalent if two conditionsare true.1. S1 and S2 must produce the same values at thestate-machine output(s)2. For each input combination, S1 and S2 must haveeither the same next state or eguivalent next states
◼ A pair of equivalent states can be replaced by a single state. ◼ Two state S1 and S2 are equivalent if two conditions are true. 1. S1 and S2 must produce the same values at the state-machine output(s) 2. For each input combination, S1 and S2 must have either the same next state or equivalent next states. The state/output table constructed in previous page is “minimal”. If the other tables with more states(e.g. P368 Figure 7-51), we need minimize the number of states in such tables. 7.4 Clocked Synchronous State-Machine Design 2. State Minimization Return Back Next