This presentation discusses register organization and the instruction cycle in a central processing unit. It describes the main types of registers in a CPU, including general purpose, address, status, and memory registers. It then explains the four main stages of an instruction cycle: 1) fetching the instruction from memory, 2) decoding the instruction, 3) reading the effective address, and 4) executing the instruction. It provides details on how the memory address register, memory data register, program counter, and instruction register are involved in transferring instructions from memory to the CPU for execution.

1. PRESENTATION DE COMPUTER
ARCHITECTURE
Topic: Register Organization & Instruction Cycle

2. MUHAMMAD AMEER MOHAVIA
BS(ELECTRONICS ENGINEERING)
BALOCHISTAN UNIVERSITY OF INFORAMTION
TECHNOLOGY ENGINEERING AND MANAGEMENT
SCIENCE’S QUETTA PAKISATN.

3. REGISTER ORGANIZATON
 A register is a very small amount of very fast memory that is
built into the CPU (central processing unit) in order to speed
up its operations by providing quick access to commonly used
values.
 Registers are normally measured by the number of bits they
can hold, for example, an 8-bit register or a 32-bit register.

4. TYPES OF REGISTERS:
 User-accessible registers
 Control/Status Register
 User-visible Registers
 General purpose Register
 Address register
 Status register
 Memory buffer register
 Memory data register
 Memory address register

5. INSTRUCTION CYCLE:
 An instruction cycle' (also called fetch-and-execute cycle,
fetch-decode-execute cycle, and FDX) is the time period
during which a computer processes a machine language
instruction from its memory or the sequence of actions that the
central processing unit (CPU) performs to execute each
machine code instruction in a program.

6.  The name fetch-and-execute cycle is commonly used. The
instruction must be fetched from main memory, and then
executed by the CPU. This is fundamentally how a computer
operates, with its CPU reading and executing a series of
instructions written in its machine language. From this arise all
functions of a computer familiar from the user's end.
 There are typically four stages of an instruction cycle that the CPU
carries out:
 1) Fetching the Instruction.
 2) Decode the Instruction.
 3) “Read the effective address”.
 4) Execute the Instruction.

7.  The Cycle is Then repeated Again
 The MAR (Memory Address Register) holds the address of the location to or
from which data are to be transferred. As can be seen from the figure above,
the connection of the MAR to the main memory is one-way or unidirectional.
 The MDR (Memory Data Register) contains the data to be written or read
out of the addressed location.

8. OPERATING STEPS:

9. OPERATING STEPS:
 1) PC is set to point to the first instruction of the program (the operating system
loads the memory address of the first instruction).
 2) The contents of the PC are transferred to the MAR (which is automatically transmitted
to the MM) and a Read signal is sent to the MM (Main Memory).
 3) The addressed word is read out of MM and loaded into the MDR.
 4) The contents of MDR are transferred to the IR. The instruction is ready to be decoded
and executed.
 5) During execution, the contents of the PC are incremented or updated to point to the
next instruction.
Example:
Enumerate the different steps needed to execute the machine instruction

10. THE END