Concepts and Values Mário Tomás Catarina Rodrigues André Rodrigues 20/05/09.
Preview of “L02 FSM.pptx” · Introduc)on*to*Structured*VLSI*Design* 3Finite*State*Machines...
Transcript of Preview of “L02 FSM.pptx” · Introduc)on*to*Structured*VLSI*Design* 3Finite*State*Machines...
Introduc)on*to*Structured*VLSI*Design*3Finite*State*Machines
Joachim Rodrigues
Lund University / EITF35/ Joachim Rodrigues 2012
Overview*
• State*Machines*• Moore*• Mealy*
• Exercise*
• The*following*slides*should*fresh*up*your*memory*
• Detailed*informa)on*on*FSM’s*is*available*in*a*sample*book*chapter*on*the*course*homepage.*
Lund University / EITF35/ Joachim Rodrigues 2012
Overview*on*FSM*
• Contain(�random�(logic(in(next1state(logic(• Used(mainly(used(as(a(controller(in(a(large(system(• Moore(vs(Mealy(output((((
Lund University / EITF35/ Joachim Rodrigues 2012
Representa)on*of*FSMs*
• State(diagram((
Lund University / EITF35/ Joachim Rodrigues 2012
Moor*vs.*Mealy*
• A(Moore(machine(produces(glitch(free(outputs.(
• The(outputs(from(a(Moore(machine(are(available(to(its(environment(for(almost(a(clock(cycle,(and(in(some(situaBons(this(may(allow(using(a(faster(cock.(
• In(some(situaBons(a(Mealy(machine(can(be(specified(and(implemented(using(less(states(because(it(is(capable(of(producing(different(outputs(in(a(given(state.(
• In(some(situaBons(a(system(using(a(Mealy(machine(can(be(faster(because(an(output(may(be(produced(immediately(instead(of(at(the(next(clock(Bck.(
Lund University / EITF35/ Joachim Rodrigues 2012
Moore*vs.*Mealy*
• Moore(
– Out(=( ( (F(Current(state)(
– Next(state(=(F(Inputs,(current(state)(
S1 Y=0
A1
A2 Y
S4 Y=1
S2 Y=0
10
01
S3 Y=1
11
A1 A2 = 00
Lund University / EITF35/ Joachim Rodrigues 2012
Moore*vs.*Mealy*
• Mealy(
– Out(=( ( (F(Inputs,(Current(state)(
– Next(state(=(F(Inputs,(Current(state)(
S1 A1
A2 Y
S4
S2 10/0
01/1
00/0
S3 11/1
10/0
11/1
01/1 A1 A2 / Y
Lund University / EITF35/ Joachim Rodrigues 2012
Moore*
FSM1 FSM2 R
A
S0 A=0
R=0 S1
A=1 R=1
R=1
R=0
• …(a(Moore(machine(is(not(able(to(produce(A1>1(unBl(the(next(clock(when(it(enters(s1(
Will be entered with next clock cycle
Lund University / EITF35/ Joachim Rodrigues 2012
Mealy*
FSM1 FSM2 R
A
S0 R=0/A=0
S1 R=1/A=1
R=1/A=1
R=0/A=0
• When(in(s0,(a(Mealy(machine(may(produce(A1>1(immediately(in(response(to(R1>1(
Lund University / EITF35/ Joachim Rodrigues 2012
• Pushing:(*({(A;(B;(B;(A(}(=>(Open(
(
• Draw(a(state(graph(for(the(Lock1FSM((10min)(
A*small*exercise*/problem*
Lock FSM
Clk
A
B Open 0
1
Lund University / EITF35/ Joachim Rodrigues 2012
Edge*Detec)on*
• A*circuit*to*detect*the*rising*edge*of*a*slow*�strobe�*input*and*generate*a*�short�*(*about**13clock*period)*output*pulse.*
*• All*FSMs*realize*an*edge*
detec)on.*• The*”output”*signal*
differs!*
Lund University / EITF35/ Joachim Rodrigues 2012
Timing*Diagram*
Lund University / EITF35/ Joachim Rodrigues 2012
• Mealy(machine(uses(fewer(states(• Mealy(machine(responds(faster(• Mealy(machine(may(be(transparent(to(glitches(
• Which(one(is(be]er?(– Types(of(control(signal(
• Edge(sensiBve(– E.g.,(enable(signal(of(counter(– Both(can(be(used(but(Mealy(is(faster(
– Level(sensiBve(• E.g.,(write(enable(signal(of(SRAM(• Moore(is(preferred(
Comparison(
Lund University / EITF35/ Joachim Rodrigues 2012
FSM*Exercise*(”Homework”)*
Marge(wants(to(install(an(alarm(that(triggers(as(soon(as(somebody(enters(the(kitchen.(The(alarm(should(have(several(alert(levels.((
• level0:(Neither(Homer(nor(Bart(is(in(the(kitchen(• level1:(Bart(but(not(Homer(is(in(the(kitchen(• level2:(Homer(but(not(Bart(is(in(the(kitchen(• level3:(Homer(and(Bart(are(in(the(kitchen(
To*detect*who*enters*or*leaves*the*kitchen*2*sensors*g1*and*g0*are*installed*in*the*door*frame*as*depicted.*The*sensors*emit*a*�1�*as*soon*as*their*reflec)on*is*interrupted.*If*Bart*enters*the*kitchen*only*g0*will*emit*a*�1�.*Homer*is*always*leaning*forward*when*he*is*entering*the*kitchen,*and,*thus,*g1*will*always*be*interrupted*before*g0.*Once*they*have*decided*to*go*into*the*kitchen*they*will*go*through*the*door.*However,*if*they*are*in*the*kitchen*they*always*can*leave,*e.g.,*level3*changes*to*level2.*The*size*of*Homers*hips*and*belly*prevent*them*from*entering*the*kitchen*simultaneously.**The*clock*frequency*is*1MHz.*
Lund University / EITF35/ Joachim Rodrigues 2012
?(