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8051 Variants

8051 is a popular microcontroller, specially among students as it’s easy to learn and grasp. Since its arrival, we’ve seen it in many different shapes and forms. In fact most of the manufacturing companies have developed their own version of the 8051 architecture thus you’ll find many different models of the same microcontroller in market. They’re generally known as variants of the 8051 microcontroller.


 

WHY DO WE NEED VARIANTS?

It’s simple. Each manufacturing company introduced some features into the basic 8051 architecture and called it their own. Selecting a micro-controller for your project is another discussion and I may write about it someday but to keep things in perspective, let’s just say it’s important to select one that has most of the components (that you require) built-in rather than external. Depending on the scope of your project (or application), you must do some research and find a variant most suitable to your needs. This way you solve most of your problems before even starting.

As a quick example, let’s assume that you need to acquire analog data and process it. The AT89C51 (most common variant of 8051) doesn’t have an internal ADC so you’ll need to attach (interface) external Analog to Digital converter (ADC) along with the necessary connections. On the contrary, the AT89C51AC3 offers a 10-bit internal ADC that you can utilize thus eliminating the need for extra hardware components and circuitry. But of course, the availability of a specific variant (that you selected after careful research) in the market accessible to you is also an important factor for consideration.

 

MOST POPULAR VARIANTS

8051 was an entry level micro-controller and is available in many different shapes – thanks to all the manufacturers. In fact it’s not feasible to enlist and discuss all its variants. I would rather talk about few and leave the rest for you to find. I just want to give you a rough sketch of the concept of different variants and why you should consider searching for them. Each variant offers some unique functionality that you may or may not require. Below is a list of commonly used variants of 8051 manufactured by Atmel. I will only highlight the key features but if you’re interested to know more, you can download the full datasheet. Also, you can click on any image to view it in full size.

 

AT89C51

  • 4 KB Re-programmable Flash memory
  • 128 bytes RAM
  • 2 counters/timers (16 bit)
  • 6 interrupt sources
  • Serial Communication Channel
  • Download AT89C51 datasheet
8051 Pin Configuration
AT89C51

 

AT89C52

  • 8 KB Re-programmable Flash memory
  • 256 bytes RAM
  • 3 counters/timers (16 bit)
  • 8 interrupt sources
  • Serial Channel
  • Download AT89C52 datasheet
AT89C52 Variant
AT89C52

 

AT89S51

  • 4 KB ISP Flash memory
  • 128 bytes RAM
  • 2 counters/timers (16 bit)
  • 6 interrupt sources
  • Full Duplex Serial Channel
  • Watchdog Timer
  • Download AT89S51 datasheet
AT89S51 Variant
AT89S51

 

 

AT89S52

  • 8 KB ISP Flash memory
  • 256 bytes RAM
  • 3 counters/timers (16 bit)
  • 8 interrupt sources
  • Full Duplex Serial Channel
  • Watchdog Timer
  • Download AT89S52 datasheet
At89S52 Variant
AT89S52

 

 

AT89C1051

  • 1 KB Re-programmable Flash memory
  • 64 bytes RAM
  • 1 counter/timer (16 bit)
  • 3 interrupt sources
  • Direct LED Drive Outputs
  • On-Chip Analog Comparator
  • Download AT89C1051 datasheet
AT89C1051 Variant
AT89C1051

 

 

AT89C2051

  • 2 KB Re-programmable Flash memory
  • 128 bytes RAM
  • 2 counters/timers (16 bit)
  • 6 interrupt sources
  • Programmable Serial UART Channel
  • Direct LED Drive Outputs
  • On-Chip Analog Comparator
  • Download AT89C2051 datasheet
AT89C2051 Variant
AT89C2051

 

AT89C4051

  • 4 KB Re-programmable Flash memory
  • 128 bytes RAM
  • 2 counters/timers (16 bit)
  • 6 interrupt sources
  • Programmable Serial UART Channel
  • Direct LED Drive Outputs
  • On-Chip Analog Comparator
  • Brown-out Detection
  • Power On Reset (POR)
  • Download AT89C4051 datasheet
AT89C4051 Variant
AT89C4051

 

AT89C55

AT89C55 Variant
AT89C55

 

These are just few examples, it’s a never ending list. All these variants may not be available in your nearest market so you’ve to verify that for yourself. However, if you’re from Pakistan, you can visit Eye-Vision Electronics. They have all these variants at very reasonable prices and can deliver them right to your doorstep! They also deal in all kinds of electronic components and you’ll hardly find anything missing. I am a regular customer and quite satisfied by their quick and reliable service.

It’s quite obvious now that each variant offers some unique functionality on its own. You can choose one for yourself according to your requirements. I may talk about these different features in my future posts (but don’t wait for it). Most of them are quite handy and crucial to success of any project so it’s always advisable to keep yourself updated with the features offered by the microcontroller you have in your possession. This way, you can have more control over your application.

 

Last but not the least, what’s your favorite variant of the 8051?

 

Faizan

Muhammad Faizan Khan is an Electrical Engineer and a Computer Geek. He is a technical guy and has more than 3 years of experience in Embedded Systems, Digital Logic Design, Computer Programming and everything else that’s logical. He mostly writes tutorials related to microcontrollers for beginners in his blog, PhaseWire.

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