COmputer organization AND ASSEMBLY LANGUAGE LECTURE 1.pdf

COmputer organization AND ASSEMBLY LANGUAGE LECTURE 1.pdf

1. By Engr. Ahsan Shah
COMPUTER ORGANIZATION

2. EXPLANATION OF COMPONENTS 01
1. CPU (Central Processing Unit)
The brain of the computer.
Executes all instructions.
CONTAINS:
ALU (Arithmetic and Logic Unit) → performs calculations
and logical decisions.
Control Unit (CU) → directs operations, manages data
flow.
Registers → high-speed storage for temporary data and
instructions. By Engr. Ahsan Shah
COMPUTER ORGANIZATION

3. 2. Memory Unit
Thynk Unlimited02
Primary Memory:
Fast and directly accessible by CPU.
Includes RAM (temporary storage) and ROM (permanent
storage).
Secondary Memory:
Used for long-term storage (Hard Disk, SSD).
Slower but larger in size. By Engr. Ahsan Shah
COMPUTER ORGANIZATION

4. 03 3. Input/Output (I/O)
Unit
Input Devices: Send data/instructions to computer
(keyboard, mouse, scanner).
Output Devices: Display or produce results (monitor,
printer, speakers).
Managed via I/O controllers or ports. By Engr. Ahsan Shah
COMPUTER ORGANIZATION

5. 4. System Bus04 The communication path between all
components:
Address Bus: Carries memory
addresses.
Data Bus: Transfers actual data.
Control Bus: Carries control and timing
signals (read/write, interrupt, clock). By Engr. Ahsan Shah
COMPUTER ORGANIZATION

6. Component Function Example
CPU
Executes
instructions
Intel Core, AMD
Ryzen
Memory
Stores data and
programs
RAM, ROM
I/O Unit
Communication
with user
Keyboard, Display
System Bus
Connects
components
Address, Data,
Control lines05
Input --> CPU <--> Memory <--> Output
|
|-- System Bus (Address + Data + Control)
VON NEUMANN
ARCHITECTURE
1.Input provides data →
2.CPU fetches instructions/data from memory →
3.Processes data via ALU →
4.Stores results back to memory →
5.Sends output to devices.
Fetch – CPU fetches the
instruction from memory.
Decode – Control Unit interprets
what the instruction means.
Execute – ALU or other units carry
out the instruction.
Store – Results are written back to
memory or a register. By Engr. Ahsan Shah
COMPUTER ORGANIZATION

7. Microprocessor
Bus Structure 06 In a microprocessor-based system, communication between the
CPU, memory, and input/output devices occurs through buses.
A bus is a set of parallel electrical lines (wires) that carry data,
addresses, and control signals among system components. +--------------------------+
| MICROPROCESSOR BUS |
+--------------------------+
/ | \
+-----------+ +-----------+ +-----------+
| Address Bus | | Data Bus | | Control Bus |
+-----------+ +-----------+ +-----------+ By Engr. Ahsan Shah
COMPUTER ORGANIZATION

8. Address Bus
The address bus is used by the CPU to specify the address (location) of the memory
or I/O device it wants to communicate with.
Direction:
Unidirectional — from CPU → Memory/I/O.
Function:
It carries the address of memory locations where data or instructions are to be fetched or stored.
If the address bus is 16-bit, the CPU can address
216=65,5362^{16} = 65,536216=65,536 (64 KB) memory locations. By Engr. Ahsan Shah
COMPUTER ORGANIZATION

9. Concept Explanation
16-bit address bus
16 wires → can make 65,536
combinations
Each combination
Represents one memory
location
Each location Stores 1 byte
Total memory 65,536 × 1 byte = 64 KB
Example: 16-bit Address Bus
If the address bus is 16-bit, the CPU can address
216=65,5362^{16} = 65,536216=65,536 memory locations
→ which equals 64 KB of memory.
Step 1: What is an Address Bus?
The address bus carries the address of the memory location that the
CPU wants to read from or write to.
The number of lines (wires) in the address bus determines how many
unique addresses the CPU can generate.
Each line (bit) can have two states:
0 or 1
So, for an N-bit address bus, the total
possible combinations (addresses) are:
2N
Step 2: For a 16-bit Address Bus
If the address bus has 16 lines,
then each line can carry a binary digit (0 or 1).
So, the total number of unique addresses the CPU can create is:
216=65,536
That means:
The CPU can access 65,536 unique memory locations.
Each memory location stores 1 byte (8 bits) of data.
Step 3: Convert 65,536 Bytes into Kilobytes
1 KB=1024 Bytes
64 KB=65,536 Bytes
Therefore, a 16-bit address bus can address 64 KB of memory.
Step 4: Example in Real Microprocessor
The Intel 8085 microprocessor has a 16-bit address bus.
Hence, it can access:
216=65,536 memory addresses
→ each address = 1 byte
→ Total accessible memory = 64 KB By Engr. Ahsan Shah
COMPUTER ORGANIZATION