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AT89c51 Microcontroller: Programming, Pinout, Features, and Alternatives

Atmel AT89 series fall under the 8-bit microcontroller family compatible with Intel 8051. Their advantages include cost-effectiveness and high flexibility when used in embedded control applications. Examples of the chip under the series are AT89C2051, AT89C51, etc. For today, we’ll discuss the AT89C51 microcontroller. 

What is the AT89C51 Microcontroller?

AT89C51 is a CMOS 8-bit microcontroller of high performance but low power. Further, it has an erasable and flashes programmable (4K bytes) EPROM.  



Manufacturers use the high-density nonvolatile memory technology of an Atmel to produce a powerful microcomputer. Moreover, it’s often conjunction with pinout and set instructions from MCS-51 industry standards. 

AT89C51 Pinout

The table below summarizes the pin configuration of AT89C51. 

At89c51 pinout 

At89c51 pinout 

Features of Microcontroller

The features and specifications of at89c51 comprise the following;

  • First, it has six interrupt sources and a 128 × 8-bit internal RAM. 
  • Then, its fully static operation via the external oscillator ranges from 0Hz to 24MHz.
  • Thirdly, it is compatible with MCS-51™ products.
  • Despite lacking comparators, DAC and in-built ADC module, and data EEPROM, it has an internal oscillator. 
  • It has a 4Kb flash memory. 
  • It also has power-down and low-power idle modes. 
  • The 40-pinned at89c51 has an operating voltage of 2V to 5.5V and an operating temperature ranging from -55°C to 125°C. 
  • Besides having a three-level program memory lock, it also has a programmable serial channel. Additionally, it has two 16-bit timers/counters and 32-programmable I/O lines. 
  • Lastly, it can endure 1000 write/erase cycles during 4K bytes of in-system reprogrammable flash memory endurance. 


They are as follows;

  • ATtiny88, 
  • ATMEga32,
  • ATMega8,

How to Program the AT89C51 (8051) Microcontroller

You can use software like Keil µVision or Arduino to program AT89C51. We’ll also need a programming environment like an Integrated Development Environment (IDE), USBASP programmer, and MAX232 programming hardware. You’ll purchase all the components separately. 

  • First, a compiler converts the software into readable HEX files. An IPE then dumps the files into MCUs for reading. 
  • Then, you can save time by simulating the software before using it on the hardware. 

How to select your Atmel Microcontroller?

Undeniably, there are several microcontrollers from Atmel and PIC families, all with advantages and disadvantages. Choosing the best one for your project, therefore, requires a good criterion. 

The list below gives examples of the factors you can consider.

  • First, ensure your MCU can support communication protocols like CAN, I2C, SPI, and UART for such projects. Some MCUs may also support two or more modules for one protocol.
  • Secondly, check on your actuators and sensors, then verify the modules your MCU may need. For instance, a supportive resolution and ADC channel in MCUs may be ideal for reading many Analog voltages. 
  • Then, smaller sizes like 8-pin MCUs, which are relatively cheaper, are suitable with a price and size limitation. 
  • In addition, choose an MCU that suits the operating voltage in your system. For example, a 3.3V MCU operates well on a system (devices or sensors) that communicate and work on 3.3V. 
  • Finally, your MCU must have wide applications and good online community support, such as Atmega338 or AT89S52. 


Some applications of at89c51 include;

  • As a replacement for the Arduino module,
Arduino UNO microcontroller

(Arduino UNO microcontroller)

  • In projects that require multiple I/O communications and interfaces, 
  • Advanced level A/D applications in consumer, appliances, industrial, and automotive applications,
  • In learning Atmel, and
  • Multiple DIY projects. 


That sums up our at89c51 article. For further inquiries or questions, kindly contact us

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Emma Lu
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