Microprocessor

A microprocessor is a small electronic device that performs the functions of a central processing unit (CPU) on
a single integrated circuit (IC). It is the brain of a computer or other digital devices, responsible for executing
instructions from a computer program by performing basic arithmetic, logic, control, and input/output (I/O)
operations.

• Performs Calculations: It can do basic math, like addition and subtraction, and make decisions based on
comparisons.

• Follow Instructions: It reads and follows a list of instructions (programs) to do specific tasks, like opening an
app or playing a video.

• Controls Parts: It tells other parts of the device what to do and when to do it,

• Stores Information Temporarily: It has small, super-fast storage areas to keep data handy while it’s working
on it.

• Speed: How fast operation can work

Microprocessor Vs Integrated Circuit (IC)
Main difference between a microprocessor and an integrated circuit is their purpose and complexity. A
microprocessor is a more complex device designed to perform general-purpose computing tasks, whereas an IC is
a more specific device designed to perform specific functions.

In fact, a CPU is often referred to as a microprocessor. All CPUs are

Microprocessor as CPU microprocessors, but not all microprocessors are CPUs????

The difference between two is

their functionality and purpose
within a computer system. A CPU
is a type of processor tasked with
a variety of roles. A
microprocessor is generally tasked
Traditional block Computer with
with one specific task and does
diagram of Computer microprocessor as CPU that one task exceedingly well.
CPU and Microprocessor

• CPU Example: Think of the CPU in your laptop. It handles everything from running your operating system to
browsing the internet and playing games.

• Non-CPU Microprocessor Example: Consider a washing machine. It has a microprocessor that controls the
washing cycles, but this microprocessor is not a CPU because it’s not running a full computer system.

Simple Analogy:
• CPU in a Computer: Like the main chef in a restaurant who oversees everything and makes complex dishes.

• Microprocessor in Other Devices: Like a kitchen appliance (e.g., a microwave) that does one specific job
(heating food).
Types of Microprocessors
Some of the common types of microprocessors include:

• General Purpose Microprocessors: These are the most common microprocessors used in computers and other
electronic devices. Examples of general-purpose microprocessors include the Intel Core series, AMD Ryzen series,
and ARM Cortex series.

• Digital Signal Processors (DSPs): These microprocessors are designed for processing digital signals such as
audio and video. They are commonly used in cell phones, digital cameras, and music players.

• Graphics Processing Units (GPUs): These microprocessors are designed for performing complex calculations
related to graphics and image processing. They are commonly used in gaming systems, video editing software, and
other applications that require high-performance graphics processing.

• System-on-Chip (SoC) Microprocessors: These microprocessors combine multiple components, such as a

microprocessor, memory, and input/output interfaces, into a single chip. They are commonly used in mobile
devices and other small electronic devices. Examples of SoC microprocessors include the Qualcomm Snapdragon
series and Apple A-series.

• FPGAs are specialized microprocessors that users can program to perform a specific task. They are commonly
used in digital signal processing, image processing, and cryptography applications.
Microprocessor as a Programming Device
Program Execution: A microprocessor follows a set of instructions written in a program. These
instructions tell the microprocessor what to do, step by step.

Flexible Functionality: Because a microprocessor can be programmed with different instructions, it

can perform a wide variety of tasks.

Example
Smartphone:

Think of your smartphone’s microprocessor. When you tap an app icon, the microprocessor runs the
program for that app, following instructions to open it, display content, and respond to your touches.

Washing Machine:
In a modern washing machine, a microprocessor might run programs that control the washing cycles. It
follows instructions to fill the machine with water, agitate the clothes, rinse, and spin.
History of Microprocessors
 Microprocessor Organization
Internally, the microprocessor is made up of 3
main units.
• Arithmetic/Logic Unit (ALU)
• Control Unit.
• An array of registers for holding data

Simplified version of Microprocessor with bus architecture

Intel 8085 is an 8 bit microprocessor introduced by Intel.

8085 has 16 bit address bus and 8 bit data bus.
It can access 216 (65536) individual memory locations (64KB)
Has built in register:
A (accumulator), B,C,D,E,H and L (8 bit)
Special purpose register: 16 bit program counter, stack pointer,
and 8 bit flag register

"80" typically denotes the series, and the "85" is the specific
model number.
Components of a Microprocessor
❑ Arithmetic and Logic Unit (ALU):
• Performs all arithmetic operations (addition, subtraction, multiplication, division).
• Handles logical operations (AND, OR, NOT, XOR).
❑ Control Unit (CU):
• Directs the flow of data between the processor and other components.
• Decodes instructions fetched from memory.
• Coordinates the execution of instructions.
❑ Registers:
• Temporarily store data or intermediate results.

❑ Bus Interface Unit (BIU):

• Manages communication between the processor and external components.
• Types of buses:
❑ Data Bus: Transfers data.
❑ Address Bus: Specifies memory addresses.
❑ Control Bus: Sends control signals (e.g., Read/Write).

❑ Clock Generator:
• Synchronizes operations of the microprocessor with a clock signal.
• Defines the speed of operation (measured in MHz or GHz).

❑ Input/Output (I/O) Interfaces:

• Facilitates communication between the processor and external devices (keyboard, mouse, sensors).
Generalized MPU
 Practice questions

1. How many address lines are needed to access 1 GB of memory?

2. What happens if the data bus is smaller than the word size of the CPU?

3. What is a multiplexed bus?

4. What is the main purpose of a clock in a microcontroller?

A. Provide power to the processor
B. Control input/output operations
C. Synchronize operations and control timing
D. Store program data
5. RESET operation is generally:
A. Hardware-based only
B. Software-based only
C. Can be hardware or software-based
D. Not used in modern microprocessors
6. What happens to the result of an ALU operation?
A. It is lost
B. It is stored in a ROM
C. It is usually stored in the accumulator or a register
D. It is printed to screen
8085 Microprocessor Architecture
8-bit general purpose µP
Addressing 64 kB of memory Has 40 pins
Requires +5 V power supply
Can operate with 3,5 and 6 MHz clock
Technology node 3 μm
Transistors 6,500
System Bus – wires connecting memory & I/O to
microprocessor
Address Bus
• Unidirectional
• Identifying peripheral or memory location
Data Bus
• Bidirectional
• Transferring data
Control Bus
• Synchronization signals
• Timing signals
• Control signal
External initiated operations
• RESET
• Interrupt
• BUS request
 External Initiated operations

• RESET
• Interrupt
• Ready
• Hold

8085 Programmable registers

MPU, Memory and I/O
How MPU executes??
MPU performs primarily four
1. To execute a program, the microprocessor “reads” each
operation
instruction from memory, “interprets” it, then “executes” it.
2. To use the right names for the cycles: – The microprocessor
• Memory read
fetches each instruction, – decodes it, – Then executes it.
• Memory write
3. This sequence is continued until all instructions are performed.
• I/O read
4. To communicate with memory and Input-output, MPU performs
• I/O write
four operations
Memory read, Memory write, I/O read, I/O write

How MPU identify Memory or I/O??

MPU identifies with a binary address called address bus

How MPU identify read or write???

Control signal
BUS organization
• Bus organization of the microprocessor is the way in which the microprocessor communicates with other
devices in a computer system.
• Is a communication path between microprocessor and peripherals. A group of wires to carry bits.
• Ex: 8085 microprocessor has a 16-bit address bus, an 8-bit data bus, and various control signals to
manage data transfer and other operations.

• Address bus –
Unidirectional bus that is used to carry the memory or I/O device address to which the data is to be
transferred.

• Data bus -
Bidirectional bus that is used to transfer data between the microprocessor and other components such as
memory and I/O devices.

• Control bus –
Bidirectional bus that is used to carry control signals between the microprocessor and other components
such as memory and I/O devices.
Example: Memory read

Bus organization

Memory is addressed by 16 bit and each memory stores 8 bit of data

Hex code and instructions

Example: Microprocessor controlled temperature system
• Explain the difference between a microprocessor and a microcomputer.
• Explain these terms: SSI, MSI, and LSI.
• Define bit, byte, word, instruction and nibble.
• How many bytes make a word of 32 bits?
• Specify the number of registers in a 2KB memory chip.
• Calculate the number of registers in a 64KB memory board.
• Explain the difference between a compiler and an interpreter.
• Difference between machine language and assembly language (8085).