What"is"state?" - PowerPoint PPT Presentation

1 2 What"is"state?" • You"see"delicious"looking"potato"salad"in"the"cafeteria?""" Do"you"eat"it?" – Ate"potato"salad"as"a"kid…Good!" EE"109"Unit"9"–"State"Machines" – As"a"teen,"ate"potato"salad"at"a"picnic"aEer"a"long"hot"day…Uh"oh!" • Your"decision"is"influenced"not"just"on"how"it"looks"now,"but" the"sum"of"all"your"previous"experiences" – The"sum"of"all"your"previous"experiences"is"what"is"known"as" state% – Your"'state'"determines"your"interpretaOon"of"your"senses"and" thoughts" • In"a"circuit,"'state'"refers"to"all"the"bits"being"remembered" (registers"or"memory)" • In"soEware,"'state'"refers"to"all"the"variable"values"that"are" being"used" 3 4 State"Machine"Block"Diagram" State"Diagrams" • A"system"that"uOlizes"state"is"oEen"referred"to"as"a"state"machine"" • Abstractly"a"state"machine"can"be"visualized"and"represented" – A.k.a."Finite"State"Machine"[FSM]" as"a"flow"chart"(or"state"diagram)" • Most"state"machines"can"be"embodied"in"the"following"form" – Circles"or"boxes"represent"state" – Logic"examines"what's"happening"NOW"(inputs)"&"in"the"PAST"(state)"to…" – Arrows"show"what"input"causes"a"transiOon" • Produce"outputs"(acOons"you"do"now)"" – Outputs"can"be"generated"whenever"you"reach"a"parOcular"state"or" • Update"the"state"(which"will"be"used"in"the"future"to"change"the"decision)" based"on"the"combinaOon"of"state"+"input" • Inputs"will"go"away"or"change,"so"state"needs"to"summarize/ State Machine to check for two consecutive 1's on a digital input capture"anything"that"might"need"to"be"remembered"and"used"in" the"future" Input=1 Input=1 Input=1 Input=0 Inputs Logic Outputs (ADC, Timer, S0 S1 S2 Buttons) Out=False Out=False out=True Input=0 State On startup Input=0 (memory)

5 6 Another"Example" Formal"DefiniOon" • Potato"salad"eaOng…Let's"let"state"represent"our"present"feeling/ • MathemaOcally,"a"state"machine"is"defined"by"a"6dtuple"(a" experience" tuple"is"just"several"pieces"of"informaOon"that"go"together):" • NoOce"I"don't"remember"every"occasion"that"I"ate"potato"salad…my"state" – A"set"of"possible"input"values" summarizes"just"enough"for"me"to"make"a"decision" – A"set"of"possible"states" – SomeOmes"two"states"with"same"output"but"it"helps"differenOate"future" – A"set"of"possible"output"values" acOon"(I"have"to"get"sick"twice)"to"not"eat"(if"I"just"had"a"posiOve"and"negaOve" state"I"would"change"my"mind"the"1st"Ome"I"got"sick)" – An"iniOal"state" – A"transiOon"funcOon:""{States"x"Inputs}"d>"the"Next"state" Bad Taste && – An"output"funcOon:"{States"x"Inputs}"d>"Output"value(s)" Not Sick Good Taste && Bad Taste || Get Sick Neutral Get Sick Positive Negative (Eat) (Don't Eat) (Eat) Bad Taste || Get Good Taste && Good Taste && Good Taste && Sick Not Sick Not Sick Not Sick 7 8 Formal"DefiniOon" Washing"Machine"State"Diagram" • MathemaOcally,"a"state"machine"consists"of:" /RESET Inputs% – A"set"of"possible"input"values:""{0,"1}" Stay in the initial state State% 0% 1% – A"set"of"possible"states:"{S0,"S1,"S2}" until there is enough COINS + DOOR Idle S0% S0" S1" money (coins) and – A"set"of"possible"outputs:"{False,"True}" N=2 the door is closed S1% S0" S2" COINS • DOOR – An"iniOal"state"="S0" S2% S0" S2" Fill – A"transiOon"funcOon:""" FULL WV = 1 • {States"x"Inputs}"d>"the"Next"state" State Transition FULL Function – An"output"funcOon:"" Agitate We move through the 5 MIN Motor = 1 states based on the • {States"x"Inputs}"d>"Output"value(s)" State% Outputs% conditions. Outputs 5 MIN / Reset_Timer=1 get asserted when the S0% False" Drain machine is in that EMPTY DV = 1 S1% False" state and the transition is true. EMPTY S2% True" N > 0 N = N - 1 Output Function N = 0

9 10 Washing"Machine"State"Diagram" Washing"Machine"State"Diagram" /RESET /RESET Move to the Fill state when there is enough COINS + DOOR COINS + DOOR Idle Idle money (coins) and Stay in the Fill state N=2 N=2 the door is closed until it is full … also COINS • DOOR COINS • DOOR set the Water Valve Open output to be Fill Fill FULL FULL true WV = 1 WV = 1 FULL FULL Agitate Agitate 5 MIN 5 MIN Motor = 1 Motor = 1 5 MIN / Reset_Timer=1 5 MIN / Reset_Timer=1 Drain Drain EMPTY EMPTY DV = 1 DV = 1 EMPTY EMPTY N > 0 N > 0 N = N - 1 N = N - 1 N = 0 N = 0 11 12 SoEware"vs."Hardware" Washing"Machine"State"Diagram" /RESET • SoEware" • Hardware" – State"="just"a"variable(s)"" – State"="Register"" COINS + DOOR Idle (DdFlipdFlops)" – Logic"="if"statements"to" N=2 update"the"next"state" – Logic"="AND/OR"Gates"to" Move to the Agitate COINS • DOOR state after it is full produce"the"next"state"&"outputs" • if(state"=="'A'"&&"input"=="1)" Fill FULL WV = 1 """{"state"="'B';"}" – TransiOons"triggered"by"clock" FULL – TransiOons"triggered"by"input" signal" Agitate or"Omers" – More%on%this%in%EE%154% 5 MIN Motor = 1 – In%EE%109,%we'll%implement% 5 MIN / Reset_Timer=1 our%state%machines%in%SW% Drain EMPTY DV = 1 Inputs Outputs Logic EMPTY (ADC, Timer, N > 0 N = N - 1 Buttons) State N = 0 (memory)