Illustrate the execute cycle, Computer Engineering

Assignment Help:

Q. Illustrate the Execute Cycle?

The fetch and indirect cycles include a small, fixed sequence of micro-operations. Every one of these cycles has fixed sequence of micro-operations which are common to all instructions. 

This isn't true of the execute cycle. For a specific machine with N different opcodes there are N different sequences of micro-operations which can occur. Let's consider some hypothetical instructions:

An add instruction which adds the contents of memory location X to Register R1 with R1 storing the result:

ADD R1, X

Sequence of micro-operations can be:

T1:  MAR ← IR (address)

T2:  MBR ← [MAR]

T3:  R1     ← R1 + MBR

At the beginning of execute cycle IR comprises the ADD instruction and its direct operand address (memory location X). At time T1 address part of the IR is transferred to MAR. At T2 the referenced memory location is read in MBR.

Lastly at T3 contents of R1 and MBR are added by ALU. 

Let's discuss one more instruction:

ISZ X it increments content of memory location X by 1. If the result is 0 the subsequent instruction in the sequence is skipped. A possible sequence of micro-operations for this instruction can be:

 T1:  MAR ← IR (address)

         T2:  MBR ← [MAR]

         T3:  MBR ← MBR+ 1

         T4:  [MAR] ← MBR

 If (MBR = 0) then (PC ← PC+ I)

Please remember that for this machine we have presumed that MBR can be incremented by ALU directly.

PC is incremented if MBR comprises 0. This test and action can be applied as one micro-operation. Please note also that this micro-operation may be executedat the time of the same time unit during which updated value in MBR is stored back to memory.


Related Discussions:- Illustrate the execute cycle

Define entry section and exit section, Define entry section and exit sectio...

Define entry section and exit section. The critical section problem is to design a protocol that the processes can use to cooperate. Every process must request permission to e

Illustrate some notations of object modeling notations, Illustrate some not...

Illustrate some notations of object modeling notations A classifier is a mechanism which describes behavioural and structural features. In UML significant classifiers are cla

Is dos a real time os, DOS is not a RTOS (real time Operating system), thou...

DOS is not a RTOS (real time Operating system), though MS DOS can be used with certain APIs to attain the RTOS functionality. For example, the RT Kernel (Real Time Kernel) which ca

What is a formal description for a programming language, A grammar for a pr...

A grammar for a programming language is a formal description of ? Structure is a formal description for a programming language.

Rule in a single direction - equivalences rules, Rule in a single direction...

Rule in a single direction - equivalences rules: Hence there the power to replace  sub expressions always allows use to prove theorems with equivalences: as given in the above

Prove equations by using the boolean algebraic theorems, Prove the equation...

Prove the equations using the Boolean algebraic theorems that is given below A‾BC + AB‾C + ABC‾+ ABC = AB + BC + AC Ans. The equation given is A‾BC + AB‾C + ABC‾+ ABC = AB + BC +

Bit pair recoding and 2’s complement, Explain bit pair recoding with an exa...

Explain bit pair recoding with an example? Ans: Bit pair recoding halves the maximum number of summands. Group the Booth-recoded multiplier bits in pairs and see the following

Determine the decimal equivalent of hexadecimal number, The hexadecimal num...

The hexadecimal number for (95.5) 10 is ? Ans. (95.5) 10 = (5F.8) 16 Integer part Fractional part 0.5x16=8.0

Or-introduction rule, Or-Introduction : Thus if we know about one thin...

Or-Introduction : Thus if we know about one thing is true, and also we know that a sentence when there thing is in a disjunction is true. Here if we consider example, like we

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd