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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

Apply social psychology on real life in Nigerian universities campus
tyosaa Reply
what is the meaning of an idiosyncratic pattern
Krystle Reply
I am here for the first time just here to learn...
michael Reply
hi I'm new on here first time
hi,am new here
what is this group all about
Suppose an individual with OCD experiences obsessive thoughts about germs, contamination, and disease whenever she encounters a doorknob. What might have constituted a viable unconditioned stimulus? 
la Reply
What are factors that influence learning?
Enos Reply
Environment Heredity(I am not sure about heredity)
Helpful. .. thanks
Sure, anytime
I have other questions also
Based on the factors affecting learning, how do we improve learning
I think that addressing that everyone learns in their own time
Peer group influence can also be another reason
Also knowing what's going on at home. what pressure are the parents putting on them.
am I close or no
also is there a lack of care? going one more step. with peer groups do an activity that shows how much they have in common
under what schedule of reinforcement do animals learn from ?
Phelisa Reply
the role of emotional intelligence in a courtship behavior
Caren Reply
describe the task and roles of industrial psychologist in solving the problems
Solomzi Reply
hi I'm Vaishnavi and I'm new to psychology:)
Vaishnavi Reply
what is motivation
Muhammad Reply
getting passionate about something and strive for success
observation and method based
Winter Reply
the meaning of science
soul is the Greek word for psyche
psychology is scientific research of the human brain.
Psychology is a study of human mind and behaviour
psychology is a social science which aim at studying the mind as it affect the behavior of an individual.
write and explain four psychosexual stages of personality development
I'm asking on behalf of someone How can a guy get over his weakness for girls? Like the person have soft spot for every girl and he thinks he love them then suddenly stuff change.... Like a switch
Ajayi Reply
whats the age of the boy?
16 or 17
lol. it gets over with time. it's not something that can be changed instantly. and for teenagers.. anyone of opposite sex is a tasty lollipop.
yes in time it will go away but could also take years
maybe because he doesn't really have mind of making decisions at the moment on what he need and what he doesn't want
maybe he's trying to find someone to love because he's either lacked loved and feel that's the only way to feel loved or he's lonely and feels a girl can make it better . either he's got deal with the core issue
its natural. I think it should be like this. girls also have weakness toward guys. but you can overcome on few things like concept of beauty. first step is realisation which will grow in you. also discipline help in these things.
what are cluster A disease?
Saee Reply
because psychology is a natural science as well as a science. it's a interdisciplinary subject
Kamakshi Reply
yes absolutely we cabt out Psychology completely into science dur to its various measuring aspects
cannot* put*
When we have data register and address registers in user mode (visible registers) then why we need MAR and MBR
Hassan Reply
with the given example MOV BX,AX describe the sequence that will be followed using instruction state diagram
Gireesh 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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