Microcontrollers are small yet powerful computing units embedded into countless everyday devices—from home appliances and wearables to automotive systems and industrial machines. Unlike full-fledged microprocessors, which require external components to function, microcontrollers are self-contained systems-on-chip (SoCs) that combine a CPU core, memory, and input/output peripherals. The purpose of a microcontroller is to handle real-time, repetitive tasks such as reading sensor values, turning motors on and off, processing user input, and controlling display outputs. They're specifically optimized for these control-based tasks, providing fast response times with low energy consumption. Microcontrollers come in various architectures and sizes—8-bit, 16-bit, and 32-bit—with popular families including the ARM Cortex-M series, AVR, PIC, and STMicroelectronics STM32. A typical microcontroller includes general-purpose I/O pins, ADCs for analog inputs, digital timers, serial communication ports (UART, SPI, I2C), and sometimes built-in wireless features like Bluetooth or Wi-Fi. These interfaces allow the microcontroller to connect seamlessly with sensors, displays, storage devices, or communication modules. For example, in a smart thermostat, a microcontroller reads the temperature sensor, compares it with the desired setpoint, and activates the heating/cooling system accordingly. The growing popularity of platforms like Arduino and Raspberry Pi Pico has made microcontrollers more accessible for students, hobbyists, and professionals. These platforms offer user-friendly development environments, libraries, and community support that drastically simplify programming and hardware interfacing. Embedded C is the most widely used language for microcontroller programming, although some ecosystems support Python or block-based coding. In the industrial world, microcontrollers are integral to embedded control systems in automation, robotics, power electronics, and telecommunications. They are used to implement everything from PWM motor control and digital filtering to safety-critical fault detection systems. Because of their reliability, low cost, and power efficiency, microcontrollers form the backbone of modern embedded electronics. To conclude, microcontrollers are essential tools for real-time control, efficient signal processing, and intelligent automation. Whether powering a simple LED circuit or managing a complex industrial controller, their adaptability and reliability continue to make them one of the most important building blocks in electronics and system design.

1. MICROCONTROLLER LAB-
8051
Balaji Ramakrishna

2. MICROCONTROLLERS
Prof.
Cherrice
Traver
ECE/CS-352:
Embedded
Microcontroller
Systems
CPU ROM
RAM
I/O
A single chip
Subsystems:
Timers, Counters, Analog
Interfaces, I/O interfaces
Memory

3. PIN DIAGRAM

4. COMMON MICROCONTROLLERS
•Atmel
•ARM
•Intel
•8-bit
•8XC42
•MCS48
•MCS51
•8xC251
•16-bit
•MCS96
•MXS296
•National Semiconductor
•COP8
•Microchip
•12-bit instruction PIC
•14-bit instruction PIC
•PIC16F84
•16-bit instruction PIC
•NEC
•Motorola
•8-bit
•68HC05
•68HC08
•68HC11
•16-bit
•68HC12
•68HC16
•32-bit
•683xx
•Texas Instruments
•TMS370
•MSP430
•Zilog
•Z8
•Z86E02

5. A
MICROPROCESSOR/CONTROL
LER
 CPU: Central Processing Unit
 I/O: Input /Output
 Bus: Address bus & Data bus
 Memory: RAM & ROM
 Timer
 Interrupt
 Serial Port
 Parallel Port

6. MICROCONTROLLER
ARCHITECTURES
CPU
Program
+ Data
Address Bus
Data Bus
Memory
Von Neumann
Architecture
CPU
Program
Address Bus
Data Bus
Harvard
Architecture
Memory
Data
Address Bus
Fetch Bus
0
0
0
2n

7. “ORIGINAL” 8051 MICROCONTROLLER
Oscillator
and timing
4096 Bytes
Program
Memory
128 Bytes
Data
Memory
Two 16 Bit
Timer/Event
Counters
8051
CPU
64 K Byte
Bus
Expansion
Control
Programmable
I/O
Programmable
Serial Port Full
Duplex UART
Synchronous
Shifter
Internal data bus
External interrupts
subsystem interrupts
Control Parallel ports
Address Data Bus
I/O pins
Serial Input
Serial Output

8. 8051 ARCHITECTURE

9.  RAM memory space allocation in the 8051
7FH
30H
2FH
20H
1FH
17H
10H
0FH
07H
08H
18H
00H
Register Bank 0
(
Stack
)
Register Bank 1
Register Bank 2
Register Bank 3
Bit-Addressable RAM
Scratch pad RAM

10.  Memory space

11. BIT ADDRESSABLE RAM
Figure 2-6
Summary
of the
8051 on-
chip data
memory
(RAM)

12. BIT ADDRESSABLE RAM

13. PROGRAM STATUS WORD (PSW)

14. ACCESSING EXTERNAL
DATA MEMORY

15. ACCESSING EXTERNAL
CODE MEMORY

16. INTERFACING WITH EXTERNAL
ROM

17. EXTERNAL MEMORY

18. EXTERNAL MEMORY TIMING
DIAGRAM

19. THE EA' (EXTERNAL ACCESS) PIN IS USED TO CONTROL THE
INTERNAL OR EXTERNAL MEMORY ACCESS.
THE SIGNAL 0 IS FOR EXTERNAL MEMORY ACCESS AND
SIGNAL 1 FOR INTERNAL MEMORY ACCESS.
THE PSEN' (PROGRAM STORE ENABLE) IS FOR READING
EXTERNAL CODE MEMORY WHEN IT IS LOW (0) AND EA IS
ALSO 0.
THE ALE (ADDRESS LATCH ENABLE) ACTIVATES THE PORT 0
JOINED WITH PORT 2 TO PROVIDE 16 BIT EXTERNAL
ADDRESS BUS TO ACCESS THE EXTERNAL MEMORY. THE ALE
MULTIPLEXES THE P0:
ALE=1 FOR LATCHING ADDRESS ON P0 AS A0-A7 IN THE
16 BIT ADDRESS BUSS, ALE=0 FOR LATCHING P0 AS DATA I/O.
P0.X IS NAMED ADX BECAUSE P0 IS MULTIPLEXED FOR
ADDRESS BUS AND DATA BUS AT DIFFERENT CLOCK TIME.
WR' PROVIDES THE SIGNAL TO WRITE EXTERNAL DATA
MEMORY
RD' PROVIDES THE SIGNAL TO READ EXTERNAL DATA AND
CODE MEMORY.

20. ACCESSING ROM USING INDEXED
ADDRESSING

21. INDEXED ADDRESSING

22. PORT 0

23. PORT1

24. PORT 2

25. PORT3

26. There are 4 8-bit ports: P0, P1, P2 and P3. All of them are dual
purpose ports except P1 which is only used for I/O. The following
diagram shows a single bit in an 8051 I/O port.
When a program writes a one byte value to a port or a single bit value
to a bit of a port, assigning the value to the port as follows:
P1 = 0x12; or P1^2=1;
P1 represents the 8 bits of port 1 and P1^2 is the pin #2 of the port 1
of 8051 defined in the reg51.h of C51, a C dedicated for 8051 family.
When data is written to the port pin, it first appears on the latch input
(D) and is then passed through to the output (Q) and through an
inverter to the Field Effect Transistor (FET).
If you write a logic 0 to the port pin(DFF Q=0), it is inverted to logic 1
and turns on the FET gate. It makes the port pin connected to ground
(logic 0).
If logic 1 is written to the port pin(DFF Q=1), , then it is inverted to a
logic 0 and turns off the FET gate. Therefore the pin is at logic 1
because it is connected to high.

27.  PORT P1 (Pins 1 to 8): The port P1 is a port dedicated for general
I/O purpose. The other ports P0, P2 and P3 have dual roles in
addition to their basic I/O function.
 PORT P0 (pins 32 to 39): When the external memory access is
required then Port P0 is multiplexed for address bus and data
bus that can be used to access external memory in conjunction
with port P2. P0 acts as A0-A7 in address bus and D0-D7 for port
data. It can be used for general purpose I/O if no external
memory presents.
 PORT P2 (pins 21 to 28): Similar to P0, the port P2 can also play a
role (A8-A15) in the address bus in conjunction with PORT P0 to
access external memory.

28.  PORT P3 (Pins 10 to 17):
In addition to acting as a normal I/O port,
 P3.0 can be used for serial receive input pin(RXD)
 P3.1 can be used for serial transmit output pin(TXD)
in a serial port,
 P3.2 and P3.3 can be used as external interrupt
pins(INT0’ and INT1’),
 P3.4 and P3.5 are used for external counter input
pins(T0 and T1),
 P3.6 and P3.7 can be used as external data memory
write and read control signal pins(WR’ and RD’)read
and write pins for memory access.