11 Arithmetic Logic Unit (ALU) Flashcards Preview

EE20021 Digital systems design > 11 Arithmetic Logic Unit (ALU) > Flashcards

Flashcards in 11 Arithmetic Logic Unit (ALU) Deck (33)
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1
Q

What is the ALU?

A

Combinational circuit

2
Q

It carries out arithmetic operations such as:

A

addition • subtraction • multiplication • others

3
Q

It carries out logic operations such as:

A

AND, OR, NAND, etc • Comparisons (>=, ==, etc

4
Q

It outputs status bits for the Flags/Status register to show:

A

Carry/borrow from add/subt operations

  • Negative results from an operation
  • Zero results from an operation
5
Q

ALU symbol

A
6
Q

The ALU employs the following for its operation:

A

Two N-bit data inputs, e.g, A and B inputs

  • One N-bit data output, e.g., Y output
  • A control input that specifies which operation to execute, e.g., F input
7
Q

Example operations performed by the ALU?

A
8
Q

Opcode

A

operation code used to let the ALU know what is the required operation.

9
Q

Mnemonics,

A

easily remembered alphabetic code for the opcode. Mnemonic is used by the Engineer, but by the ALU.

10
Q

machine language

A

ALU understand machine language

11
Q

What is the status register?

A

The status register contains information about the state of the microprocessor after an operation has been executed.

The status register allows the program to take a certain action based on a particular condition that resulted from a previous instruction

12
Q

Common flags?

A
13
Q

The Common instruction set of the microprocessor? ALU or Register operation

A
14
Q

Instruction Set of the microprocessor

A
15
Q

What does an instruction set do/contain?

A
16
Q

Example of 16 bit instruction format

A
17
Q

Microoperations.

A

Instructions can be specified with a set of elementary/low-level operations know as Microoperations.

Microoperations are described using Register Transfer Notation (RTN) or Register Transfer Language (RTL).

18
Q

Common microoperations?

A

LOADX

STOREX

ADDX

JUMPX

19
Q

LOAD X

A
20
Q

STORE X

A
21
Q

ADD X

A
22
Q

JUMP X

A
23
Q

Assembler

A

Assembler programs are responsible for this conversion into machine language or machine code

24
Q

Instruction storage format

A
25
Q

Instruction format with two operands

A
26
Q

RISC (Reduced Instruction Set Computer): A microprocessor with a small number of simple instructions.

A
  • Large number of general purpose registers
  • Simple instructions that execute quickly
  • Each instruction performs one operation
  • Instructions performs one operation
  • Instructions have a fixed size
  • Operations are performed between registers
27
Q

CISC (Complex Instruction Set Computer): A microprocessor with a large number of instructions that perform complex computations.

A

Large number of instructions

Instructions of variable length

A single instruction performs multiple operations

Complex operations required more than one clock cycle

Require multiple clock cycles which slows down the performance

28
Q

Multiplication in RISC?

A
29
Q

Multiplication in CISC?

A
30
Q

Abstraction: Assembly language

A

Assembly language

  • Programming language
  • Use of mnemonic and operands
  • Opcode and address
31
Q

Abstraction levels: Instruction set Architecture

A

Instruction Set Architecture

  • Instructions that a computer is able to perform
  • Each instruction is specified by microoperations
  • Microoperations are low-level instructions represented with Register Transfer Notation
32
Q

Abstraction Machine language/Code

A

Machine language/code

• Language compose of 0s and 1s that the computer is able to understandable

33
Q
A