• Dhanush kumar S

Microcontrollers in Embedded Systems

Updated: Aug 29, 2020

An embedded system is defined as the #integration of computer memory, processor, and input/output peripheral devices designed to perform a particular task in a given time. The Embedded system is a cornerstone of the #electronics industry. The complexity of an embedded system depends on the task to which it has been assigned. The usage of the #embeddedsystems ranges from mobile phones, digital watches to traffic light controllers, and avionics.

The core of embedded systems is the microcontrollers. It can also be called the CPU of the embedded systems as it controls the functioning of the whole system. This article briefly explains the configurations of microcontrollers and it's working.


A microcontroller is a single-chip #VLSI unit that possesses enhanced input/output capability and performs a single task. RAM, ROM and I/O ports should be embedded together on a chip and cannot be added externally.

The cost of manufacturing is less and also possesses lightweight, when compared to other processors. It has fixed I/O ports and memory space that can perform limited tasks. It also consumes low power.

There are certain criteria for choosing microcontrollers for the respective embedded systems. They are speed, power consumption, cost per single unit, mode of packaging whether it is a Dual Inline Package[DIP] or Quad Flat Package[QFP], number of I/O ports and the amount of RAM and ROM.

The microcontroller family of 8051 is mostly used in embedded systems. Intel allowed other manufactures to construct different flavors or modules of 8051. If we write a code for one module of 8051, it can run on other modules too. This paved a way for manufacturing several versions with different speeds and amount of on-chip RAM. The 8051 family consists of 8052 and 8031 microcontrollers.

Microcontroller 8052

The 8052 single-chip microcontrollers were developed by Intel to use in embedded systems. It is commonly identified as 'Big brother' of 8051 microcontrollers. 8052 microcontroller possesses 8 kb of on-chip program ROM and 256 bytes of RAM. It has 3 timers, 8 interrupt sources, and 255 operation codes. These microcontrollers, possess 32 I/O pins and 1 serial port to receive and transmit serial data.

The 8052 microcontrollers were designed such that control of MCU and all input/output between the MCU and external devices is attained through Special Function Registers (SFR).

Each SFR has an address between 128 and 255. Additionally, it has all the features of the traditional 8051 microcontrollers. 8051 is a subset of 8052 microcontrollers.

Microcontroller 8031

Intel 8031 and 80C31 are the members of the Intel MCS-51 family of 8-bit microcontrollers. This controller is often referred to as, ROM-less 8051 as it possesses 0 kb of ROM and that has to be connected externally. The size of the RAM is about 128 bytes. It has 2 timers and 6 interrupt sources, and 1 serial port.

Intel 80C31 which is the C-MOS version of 8031 N-MOS microcontrollers, completely pins and object code compatible with 8031. The 80C31 version consumes less #power when compared to its N-MOS version.

  • The idle mode may turn off the CPU core but keeps the peripherals and RAM active.

  • The power-down mode turns off CPU and peripherals and keeps only RAM #memory active.

  • Advanced Micro Devices (AMD), Intel, and Signetics are the three main manufacturers of 8031 microcontrollers.

But mostly, this 8031 is not employed because of its external ROM and it occupies 2 ports. And the program which is to be fed should also be within the size of 64 kb.

Microcontrollers 8051

The 8051 microcontrollers are referred to as " System on a chip" because of its various advanced features. It has 4 kb of on-chip program memory[ROM] and 128 bytes of data memory [RAM]. It has 2 timers and 6 interrupt sources.

One important feature is, it has an 8-bit bidirectional data bus and 16-bit unidirectional address bus. It also possesses a 16-bit data pointer. The attributes such as UARTs, Analog to digital converters, an op-amp can also be interfaced with this 8051 module.

An on-chip crystal oscillator is integrated into the microcontroller having a crystal frequency of about 12MHz. It also possesses power-saving mode in it. One specific feature of 8051 is the inclusion of the Boolean processing engine.

It allows bit-level boolean logic operations to be carried directly on internal registers, ports, and selected RAM locations. It also has four bank selectable working register sets that can reduce the time required for the context switches to enter and leave the interrupt service routines.

8051 variants include on-chip oscillators, self-programmable FLASH ROM memory, bootloader code in ROM, PWM generators, analog comparators, Bluetooth radio modules and several other components that help in the smooth functioning of the controller.


  • 8051 microcontrollers are available as discrete parts and they are widely employed as Silicon Intellectual property cores.

  • They are also available in hardware description language codes such as Verilog and FPGA netlist forms. These cores are used in the manufacturing of several embedded systems.

  • Due to the small size and low power consumption property of 8051 silicon IP cores they are used in products starting from USB flash drives to washing machines.

  • They are also employed in complex wireless communication systems on a chip.

  • In the manufacturing of handy medical gadgets such as glucose and blood pressure monitors, the 8051 controllers are used. They process the data and helps us to view the result with more accuracy.

  • In automobiles, cruise power and anti-break mechanism are controlled by 8051. It is also extensively used in hybrid motor vehicles to control the engine variations.

  • In this modern era of technology, touch sensing abilities are integrated with microcontrollers. Transportable devices such as gaming devices, LCD, or LED televisions, mobile phones are some of the products of this.

  • 8051 controller is also used in the electric meters that measure the current consumption in any domestic or in the industrial areas.

Apart from the above-mentioned applications, there are also several uses existing for 8051 microcontrollers. In almost all the electrical appliances that we use in our day-to-day life the contribution of microcontrollers especially 8051 is present.

The family of 8051 microcontrollers is mostly employed in the manufacturing of embedded systems. The usage of microcontrollers is still increasing because of its benefits and simplicity.

See also:

  1. The Architecture of Embedded Systems

  2. Microprocessors in Embedded Systems

  3. Tools in Embedded Systems

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