What is the 8051 Microcontroller?

History of 8051 Microcontroller

The 8051 Microcontroller Introduction provides a brief history of the 8051 Microcontroller. The Intel 8051 Microcontroller (Intel MSC-51 Architecture) succeeded the Intel 8048 Microcontroller (Intel MSC-48 Architecture). Although CMOS technology (which is renowned for its low power consumption) is now used in 8051 microcontrollers, they were originally designed to employ N-MOS technology due to battery-powered devices’ low power requirements. While Intel produced 8051 microcontrollers (which were ceased production in 2007), 8051 compatible microcontrollers, or processors based on the MSC-51 architecture, are now produced by more than 20 semiconductor vendors.

Among the 8051 microcontrollers produced by various manufacturers are those from Atmel (AT89C51, AT89S51), Phillips (S87C654), STC Micro (STC89C52), Infineon (SAB-C515, XC800), Siemens (SAB-C501), Silicon Labs (C8051), NXP (NXP700, NXP900), etc. The majority of contemporary 8051 microcontrollers are silicon IP Cores (Intellectual Property Cores), but discrete 8051 microcontroller ICs are also offered. Due to its low power consumption, compact design, and simple architecture, 8051 IP Cores are preferred over MCUs based on Advanced ARM Architecture for FPGAs and SoCs.

8051 Microcontroller

What is 8051 Microcontroller?

The Intel MCS-51 Architecture, also known as the 8051 microcontroller series, was created by Intel in 1980 and was (and continues to be) immensely popular during that decade.

The 8051 Microcontroller stands as an eminent and frequently employed microcontroller across diverse domains, encompassing embedded systems, consumer electronics, automobiles, and more. numerous students and beginners start their work on the 8051 Microcontroller principle of Microcontrollers since it has numerous features, including Serial Communication, Timers, Interrupts, etc. (although this trend seems to have changed with the arrival of Arduino).

8051 Microcontroller

Despite the somewhat antiquated appearance of the 8051 Microcontroller, we firmly believe that delving into Microcontrollers, Embedded Systems, and Programming offers some of the most optimal entryways into learning C and Assembly. As a result, this article will provide an overview of 8051 microcontrollers as well as some of their principles.

But first, let’s briefly discuss what a microcontroller is and how it differs from a microprocessor before moving on to the introduction and fundamentals of the 8051 microcontroller.

Structure of 8051 Microcontroller

8051 Microcontroller Pinout:

8051 Microcontroller


The Central Processor Unit, or CPU, is the brain of every processing computer, as you may already be aware. Both of the processes that are carried out by the microcontroller are examined and managed. The operator has no influence over how the CPU functions. It interprets, executes, and completes every program stored in ROM while carrying out the intended task. The CPU of 8051 microcontrollers keeps an eye on a variety of register types.


The microcontroller must include I/O (input/output) interface ports so that we can connect it to other tools, gadgets, or peripherals. Four input/output ports on the microcontroller 8051 enable this connection to peripheral devices. Timers/Counters: Micro-controller 8051 is compatible with two 16-bit counters and timers. 8-bit registers would be created from the counters. Timers are used to compute pulse duration, intervals, and other things.

For this purpose, the Microcontroller 8051 has an on-chip oscillator that serves as a CPU (Central Processing Unit) time source. Harmonized employment of all 8051 Microcontroller elements is advocated because the oscillator’s efficiency thumps are steady as a result. As is well known, the microcontroller manages the operations of the devices in embedded systems.


In its most basic form, a bus is a group of wires that serves as a contact channel or a medium for transferring data. These buses have 8, 16, or more wires in them. Either 8 bits or 16 bits will be carried by a bus overall. There are two distinct bus types:

  • Bus Address: The 16-bit bus address of the 8051 microprocessor. It is utilized for resolving memory locations. It frequently serves as a means of sending addresses from the Central Processing Unit to Memory.
  • Data bus: An 8-bit data bus is a feature of the 8051 microprocessor. It’s employed in data transporting.


As stated in the headline, an interrupt is a subroutine call that reads the microcontroller’s primary task or function and permits it to run any further crucial programs. 8051 The feature of Interrupt is quite beneficial because it helps in emergencies. One can use interrupts as a way to delay or stop the present operation, carry out a sub-routine task, and then resume the regular program’s execution.

The configuration of the 8051 Microcontroller should be such that it momentarily initiates an interruption or pause in the main program when an interrupt occurs. As soon as the sub-routine assignment is complete, the main program’s execution resumes as usual. There are five interrupt sources in the 8051 microcontroller, two of which are peripheral interrupts, two are timer interrupts, and one is a serial port interrupt.


It is software that consists of a series of instructions and calls for a microcontroller. This software assists the microcontroller in carrying out specific tasks. Such programs need a storage area where the Microcontroller may store them and interpret them to carry out a specific task. Program memory or code memory is the term for the memory used by the microcontroller device to generate. It is often referred to as ROM, or Read-Only Memory.

For the time being, the microcontroller still needs memory to store operands or data. We employ Random Access Memory, often known as RAM, for this main function. Data Memory is the term for the disk space that is used to temporarily store data for service. The 8051 microcontroller has 128 bytes of RAM and 4K of code memory, or program memory. It also has 4KB of ROM.

8051 Microcontroller Features

  • I/O ports: The 8051 features four bidirectional, 8-bit, bit-addressable input/output ports.
  • Two 16-bit timers and counters are present in the 8051.
  • 8051 is supported by the serial port’s full duplex UART connectivity.
  • 8051 External Memory The microcontroller may simultaneously access two 16 bit address lines, one for each RAM and ROM. The total amount of external RAM and ROM that an 8051 microcontroller may access is 64KB (216 for each kind).
  • Bit ALU: The Arithmetic Logic Unit, or ALU, is the brains of a microcontroller. It performs arithmetic and bitwise operations on binary numbers. The 8051 ALU can process 8-bit data operations since it is an 8-bit ALU.
  • 8-Bit Accumulator: The Accumulator is a fundamental register for the ALU. In the 8051, an accumulator is an 8-bit register.
  • RAM: 8051 The microcontroller has 128 bytes of RAM in addition to SFRs and Input/Output Port Registers.
  • ROM: The 8051 contains a 4 KB (Program Memory) on-chip ROM.

8051 Microcontroller Applications

  • Aeronautical and Space
  • Medical Equipment
  • Defense Systems
  • Robotics
  • Industrial Process and Flow Control
  • Radio and Networking Equipment
  • Remote Sensing
  • Consumer Appliances
  • Communication Systems
  • Home Applications

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