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1. basis concepts

  • Micro-operations: We have already seen that the programs are executed as a sequence of instructions, each instruction consists of a series of steps that make up the instruction cycle fetch, decode, etc. Each of these steps are, in turn, made up of a smaller series of steps called micro-operations.
  • Micro-operation execution: Each step of the instruction cycle can be decomposed into micro-operation primitives that are performed in a precise time sequence. Each micro-operation is initiated and controlled based on the use of control signals / lines coming from the control unit.

- Controller the data to move from one register to another

- Controller the activate specific ALU functions

  • Micro-instruction: Each instruction of the processor is translated into a sequence of lower-level micro-instructions. The process of translation and execution are to as microprogramming
  • Microprogramming: The concept of microprogramming was developed by Maurice Wilkes in 1951, using diode matrices for the memory element. A microprogram consist of a sequence of micro-instructions in a microprogramming.
  • Microprogrammed Control Unit is a relatively logic circuit that is capable of sequencing through micro-instructions and generating control signal to execute each micro-instruction.
  • Control Unit: The control Unit is an important portion of the processor.

The control unit issues control signals external to the processor to cause data echange with memory and I/O unit. The control Unit issues also control signals internal to the processor to move data between registres, to perform the ALU and other internal operations in processor. In a hardwired control unit, the control signals are generated by a micro-instruction are used to controller register transfers and ALU operations. Control Unit design is then the collection and the implementation of all of the needed control signals for the micro-instruction executions.

2. control unit design approaches

How can we use the concept of microprogramming to implement a Control Unit ? There are two approaches of Control Unit Design and implementation:

- Microprogrammed implementation

- Hardwired logic implementation

The figure 7.2 illustrated the control unit inputs. Two techniques have been used to implemente the CU. In a hardwired implementation, the control unit is essentially considered as a logic circuit. Its input logic signals are transformed into the set of ouput logic signals, which are the control signals. The approach of microprogrammed implementation is studied in this section.

Figure 7.2 Control unit with decoded inputs

2.1 approach of microprogrammed control unit


- The control signal values for each microoperation are stored in a memory.

- Reading the contents of the control store in a prescribed order is equivalent to sequencing through the microoperations

- Since the “microprogram” of microoperations and their control signal values are stored in memory, this is a microprogrammed unit.


  • Are more systematic with a well defined format?
  • Can be easily modified during the design process?
  • Require more components to implement
  • Tend to be slower than hardwired units (due to having to perform memory read operations)

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Computer architecture. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10761/1.1
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