Programming Model 1 Tutorial Solutions PDF

Preview

Summary

Download Programming Model 1 Tutorial Solutions PDF

Description

ProgrammingModel1 A.Introduction Objectives Attheendofthislabyoushouldbeableto:   



UsetheCPUsimulatortocreatebasicCPUinstructions UsethesimulatortoexecutebasicCPUinstructions UseCPUinstructionstomovedatatoregisters,comparevaluesinregisters, pushdatatothestack,popdatafromthestack,jumptoaddresslocations andaddvaluesheldinregisters. ExplainthefunctionsofspecialCPUregisterssuchasthePC,SRandSP registers.

B.Processor(CPU)Simulators Thecomputerarchitecturetutorialsaresupportedbysimulators,whicharecreated tounderpintheoreticalconceptsnormallycoveredduringthelectures.The simulatorsprovidevisualandanimatedrepresentationofmechanismsinvolvedand enablethestudentstoobservethehiddeninnerworkingsofsystems,whichwould bedifficultorimpossibletodootherwise.Theaddedadvantageofusingsimulators isthattheyallowthestudentstoexperimentandexploredifferenttechnological aspectsofsystemswithouthavingtoinstallandconfiguretherealsystems.

C.BasicTheory TheprogrammingmodelofcomputerarchitecturedefinesthoselowͲlevel architecturalcomponents,whichincludethefollowing   

CPUinstructionset CPUregisters Differentwaysofaddressinginstructionsanddataininstructions

 Italsodefinesinteractionbetweentheabovecomponents.ItisthislowͲlevel programmingmodelwhichmakesprogrammedcomputationspossible. 

D.SimulatorDetails Thissectionincludessomebasicinformationonthesimulator,whichshouldenable thestudentstousethesimulator.Thetutor(s)willbeavailabletohelpanyone experiencingdifficultyinusingthesimulator.Thesimulatorforthislabisan applicationrunningonaPCrunningMSWindowsoperatingsystem. Themainwindowiscomposedofseveralviews,whichrepresentdifferentfunctional partsofthesimulatedprocessor.TheseareshowninImage1belowandare composedof

1

    

CPUInstructionmemory SpecialCPUregisters CPU(generalpurpose)registers Programstack Programcreationandrunningfeatures



CPUInstruction memoryview Addprogram instructionstab  Createprogramtab

CPUregistersview

SpecialCPU registersview

Programlistview

Programstackview

Image1–CPUSimulatorwindow Thepartsofthesimulatorrelevanttothislabaredescribedbelow.Pleasereadthis informationcarefullyandtrytoidentifythedifferentpartsontheCPUSimulator windowBEFOREattemptingthefollowingexercises.Usethisinformationin conjunctionwiththeexercisesthatfollow.

2

1.CPUinstructionmemoryview Image2ͲInstructionmemory view  Thisviewcontainstheprogram instructions. The instructions are displayed as sequences of lowͲlevel instruction mnemonics (assemblerͲlevel format)andnotasbinarycode. This is done for clarity and makes code more readable by humans.  Each instruction is associated with two addresses: the physicaladdress(PAdd)andthe logical address (LAdd). This view also displays the base address (Base) against each instruction. The sequence of instructions belonging to the same program will have the samebaseaddress.

2.SpecialCPUregistersview ThisviewshowsthesetofCPUregisters,

Image3ͲSpecialCPU registersview

whichhavepreͲdefinedspecialistfunctions: PC:ProgramCountercontainstheaddress ofthenextinstructiontobeexecuted. IR:InstructionRegistercontainsthe instructioncurrentlybeingexecuted. SR:StatusRegistercontainsinformation pertainingtotheresultofthelastexecuted instruction. SP:StackPointerregisterpointstothevalue maintainedatthetopoftheprogramstack (seebelow). BR:BaseRegistercontainscurrentbase address. MAR:MemoryAddressRegistercontains thememoryaddresscurrentlybeing accessed. Statusbits:OV:Overflow;Z:Zero;N: Negative 3

3.CPUregistersview

Image4– CPURegistersview The register set view shows the contents of all the generalͲpurpose registers, which are used to maintain temporary values as the program's instructionsareexecuted.Registersare very fast memories that hold temporary values while the CPU executesinstructions.  Thisarchitecturesupportsfrom8to64 registers. These registers are often used to hold values of a program's variables as defined in highͲlevel languages.  Not all architectures have this many registers. Some have more (e.g. 128 register) and some others have less (e.g. 8 registers). In all cases, these registersservesimilarpurposes.  Thisviewdisplayseachregister'sname (Reg),itscurrentvalue (Val)andsome additional values, which are reserved for program debugging. It can also be used to reset the individual register values manually which is often useful for advanced debugging. To manually changearegister’scontent, firstselect the register then enter the new value inthetextbox,RegValue, andclickon the CHANGE button in the Registers tab.

4

4.Programstackview Image5ͲProgramstackview  Theprogramstack is anotherareawhich maintains temporary values as the instructions are executed. The stack is a LIFO(lastͲinͲfirstͲout)datastructure.It is often used for efficient interrupt handling and subͲroutine calls. Each programhasitsownindividualstack.  TheCPUinstructionsPSH(push)andPOP are used to store values on top of stack and pop values from top of stack respectively. 

5.Programlistview Image6 Ͳ ProgramListView

Use the REMOVE PROGRAM button to remove the selected program from the list; use the REMOVE ALL PROGRAMS buttontoremoveall theprogramsfrom the list. Note that when a program is removed, its instructions are also removed from the Instruction Memory Viewtoo.

6.Programcreation Image7 – Createprogramtab

Tocreateanewprogramenterits nameintheProgramNamebox anditsbaseaddressintheBase AddressboxthenclickontheADD button.Thenewprogram’sname willappearintheProgramListview (seeImage6).

5

Image8–Addprogram instructionstab Use ADD NEW… button to add a new instruction; use EDIT… button to edit the selected instruction; use MOVE DOWN/ MOVE UP buttons to move the selected instruction down or up; use INSERT ABOVE…/INSERT BELOW…buttonstoinsert anew instruction above or below the selectedinstructionrespectively.

E. Lab Exercises - Investigate and Explore Thelabexercisesareaseriesofactivities,whicharecarriedoutbythestudents underbasicguidelines.So,howisthistutorialconducted?Thestudentsareexpected tofollowtheinstructionsgiveninordertoidentifyandlocatetherequired information,toactuponitandmakenotesoftheirobservations.Inordertobeable todotheseactivitiesyoushouldconsulttheinformationinSectionDaboveandalso frequentlyrefertotheAppendixforinformationonvariousCPUinstructionsyouwill beaskedtocreateanduse.Remember,youneedtocarefullyreadandunderstand theinstructionsbeforeyoucanattempteachactivity.  Now,letusstart.FirstyouneedtoplacesomeinstructionsintheInstruction MemoryView(seeImage2),representingtheRAMintherealmachine,before executinganyinstructions.Todothis,followthestepsbelow: IntheProgramtab(seeImage7),firstenteraProgramName,andthenenteraBase Address(thiscanbeanynumber,butforthisexerciseuse100).ClickontheADD button.AnewprogramnamewillbeenteredintheProgramListview(seeImage6). YoucanusetheSAVE…buttontosaveinstructionsinafile.Youcanalsousethe LOAD…buttontoloadinstructionsfromafile. YouarenowreadytoenterinstructionsintotheCPUSimulator.Youdothisby clickingontheADDNEW…buttonintheInstructionstab(seeImage8).Thiswill displaytheInstructions:CPU0window.Youusethiswindowtoselectandenterthe CPUinstructions.Appendixlistssomeoftheinstructionsthissimulatorusesandalso givesexamplesoftheirusage. Now,haveagoatthefollowingactivities(enteryouranswersinthetextboxes provided).Awordofcaution:Regularlysaveyourcodeinafileincasethesimulator crashesinwhichcaseyoucanrestartthesimulatorandreͲloadyourfile.

6

 1. Createaninstruction,whichmovesnumber5toregisterR00. MOV #5, R00 2. Executetheaboveinstruction(todothissimplydoubleclickonitinthe InstructionMemoryView).ObservetheresultintheCPURegistersview(Image 4). 3. Createaninstruction,whichmovesnumber8toregisterR01. MOV #8, R01 4. Executeit(YoudothisbydoubleͲclickingontheinstruction) 5. ObservethecontentsofR00andR01intheCPURegistersview(Image4). 6. Createaninstruction,whichaddsthecontentsofR00andR01. ADD R00, R01 7. Executeit. 8. Observewhichregistertheresultisputin. R01 9.

Createaninstruction,whichpushestheaboveresulttothetopof thehardwarestack,andthenexecuteit. PSH R01 

10. CreateaninstructiontopushnumberͲ2ontopofthestackandexecuteit. ObservethevalueinProgramStack(Image5).  PSH #-2 11. ObservethevalueintheSPregister(SpecialCPURegistersview–Image3). WheneveryoupushavalueonProgramStack,theSPregisterisupdated.  It increments, keeps pointing to the top of the stack.  12. CreateaninstructiontocomparethevaluesinregistersR00andR01.

7

CMP R00, R01 13. Executeit. 14. ObservethevalueintheSRregister(SpecialCPURegistersview–Image3). The negative status flag is not checked.  15. ObservethestatusoftheOV/Z/Npartsofthestatusregister.Whichboxesare checkedandwhicharenot?Whatdotheyindicate? None of the boxes is checked. OV - overflow, Z - Zero, N - Negative 16. Createaninstructiontounconditionallyjumptothefirstinstruction. JMP 0 17. Executeit. 18. ObservethevalueinthePCregister.Thisistheaddressofthenextinstructionto beexecuted.Makeanoteofwhichinstructionitispointingto? 0  19. ObservethevaluesinthePAddandLAddcolumns.Whatdothesevalues indicate?Aretheydifferent(Hint:CheckouttheBaseAddressvalue)?  Physical address and the logical adress. Logical is from the perspective of the program. Physical from the perspective of the hardware. 20. WhatisthedifferencebetweentheLAddvalueofthefirstinstructionandthe LAddvalueofthesecondinstruction?Whatdoesthisvalueindicate(Hint:Think oftheinstructionlengthsinbytes)? It is the instruction length in bytes.  21. CreateaninstructiontopopthevalueontopoftheProgramStackintoregister R02. POP R02

8

22. Executeit. 23. ObservethevalueintheSPregister.  It decrements, since the stack is smaller. 24. CreateaninstructiontopopthevalueontopoftheProgramStackintoregister R03. POP R03  25. Executeit. 26. ObservethevalueintheSPregister. It's back where we started.  27. Executethelastinstructionagain.Whathappened?Explain. Stack underflow error. The stack is empty, so it cannot pop any values from the stack. 28. Createacompareinstruction,whichcomparesvaluesinregistersR04andR05. CMP R04, R05 29. ManuallyinserttwoequalvaluesinregistersR04andR05(Image4). 30. Oneagainexecutethecompareinstructioninstep28above. 31. WhichofthestatusflagsOV/Z/Nisset(i.e.boxischecked)?Why? The Z status flag is checked. When subtracted the result is zero. 32.

ManuallyinsertavalueinregisterR05greaterthanthatinregisterR04.

33.

Executethecompareinstructioninstep28above.

34.

WhichofthestatusflagsOV/Z/Nisset?Why?  Not one is checked. Because the result is not zero nor negative.

35.

ManuallyinsertavalueinregisterR04greaterthanthatinregisterR05.

36.

Executethecompareinstructioninstep28above.

37.

WhichofthestatusflagsOV/Z/Nisset?Why?

9

Now the N flag is set, because when R04 is subtracted from R05, the the result is negative. 38.

Createaninstruction,whichwilljumptothefirstinstructionifthevaluesin registersR04andR05areequal. JEQ 0

39.

TesttheaboveinstructionbymanuallyputtingequalvaluesinregistersR04 andR05,thenfirstexecutingthecompareinstructionfollowedbyexecutingthe jumpinstruction(Remember:YouexecuteaninstructionbydoubleͲclickingon it).Diditwork?

 40.

SavetheinstructionsintheInstructionMemoryViewinafilebyclickingon theSAVE…button(Image7). 

***Endofexercises***

10

Appendix - Simulator Instruction Sub-set Instruction

Description

Data transfer instructions Move data to register; move register to register MOV

e.g. MOV #2, R01 moves number 2 into register R01 MOV R01, R03 moves contents of register R01 into register R03

LDB

Load a byte from memory to register

LDW

Load a word (2 bytes) from memory to register

STB

Store a byte from register to memory

STW

Store a word (2 bytes) from register to memory Push data to top of hardware stack (TOS); push register to TOS

PSH

e.g. PSH #6 pushes number 6 on top of the stack PSH R03 pushes the contents of register R03 on top of the stack Pop data from top of hardware stack to register e.g.

POP

POP R05 pops contents of top of stack into register R05 Note: If you try to POP from an empty stack you will get the error message “Stack overflow”.

Arithmetic instructions Add number to register; add register to register e.g. ADD

ADD #3, R02 adds number 3 to contents of register R02 and stores the result in register R02. ADD R00, R01 adds contents of register R00 to contents of register R01 and stores the result in register R01.

SUB

Subtract number from register; subtract register from register

MUL

Multiply number with register; multiply register with register

DIV

Divide number with register; divide register with register

Control transfer instructions JMP

Jump to instruction address unconditionally

11

e.g. JMP 100 unconditionally jumps to address location 100 JLT

Jump to instruction address if less than (after last comparison)

JGT

Jump to instruction address if greater than (after last comparison) Jump to instruction address if equal (after last comparison instruction) e.g.

JEQ

JEQ 200 jumps to address location 200 if the previous comparison instruction result indicates that the two numbers are equal, i.e. the Z status flag is set (the Z box will be checked in this case).

JNE

Jump to instruction address if not equal (after last comparison)

CAL

Jump to subroutine address

RET

Return from subroutine

SWI

Software interrupt (used to request OS help)

HLT

Halt simulation

Comparison instruction Compare number with register; compare register with register e.g. CMP #5, R02 compare number 5 with the contents of register R02 CMP R01, R03 compare the contents of registers R01 and R03 CMP

Note: If R01 = R03 then the status flag Z will be set, i.e. the Z box is checked. If R03 > R01 then non of the status flags will be set, i.e. none of the status flag boxes are checked. If R01 > R03 then the status flag N will be set, i.e. the N status box is checked.

Input, output instructions IN

Get input data (if available) from an external IO device

OUT

Output data to an external IO device

12...