89C51 or AT89C51 is an 8-bit microcontroller and belongs to Atmel’s family . Pdf of AT89C51 datasheet & pin diagram are also available at Engineers. Disclaimer: Whilst information is supplied in good faith, we are not liable for any errors or omissions. Please consult the relevant Atmel datasheet. E&OE. Key. 89C51/89C52/89C54/89C 80C51 8-bit microcontroller family. 4K/8K/16K/32K Flash. Product specification. Replaces Datasheets 89C51 of.

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In modern terminology, it is similar to, but less sophisticated than, a system on a chip SoC ; an SoC may include a microcontroller as one of its components. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications consisting of various discrete chips.

Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, toys and other embedded systems. Mixed signal microcontrollers are common, integrating analog components needed to control non-digital electronic systems.

In the context of the internet of thingsmicrocontrollers are an economical and popular means of data collectionsensing and actuating the physical world as edge devices. Some microcontrollers may use four-bit words and operate at frequencies as low as 4 kHz, for low power consumption single-digit milliwatts or microwatts.

They generally have the ability to retain functionality while waiting for an event such as a button press or other interrupt ; power consumption while sleeping CPU clock and most peripherals off may be just nanowatts, making many of them well suited for long lasting battery applications.

Other microcontrollers may serve performance-critical roles, where they may need to act more like a digital signal processor DSPwith higher clock speeds and power consumption. The first microprocessor was the 4-bit Intel released inwith the Intel and other more capable microprocessors becoming available over the next several years.

However, both processors required external chips to implement a working system, raising total system cost, and making it impossible to economically computerize appliances.

Atmel 89C51 Microcontroller

nicrocontroller One book credits TI engineers Gary Boone and Michael Cochran with the successful creation of the first microcontroller in The result of their work was the TMSwhich became commercially available in Partly in response to the existence of the single-chip TMS[2] Intel developed a computer system on a chip optimized for control applications, the Intelwith commercial parts first shipping in This chip would find its way into mifrocontroller one billion PC keyboards, and other numerous applications.

At that time Intel’s President, Luke J. Datashee microcontrollers at this time had concurrent variants. Datasheey had EPROM program memory, with a transparent quartz window in the lid of the package to allow it to be erased by exposure to ultraviolet light, often used for prototyping. The other was either a mask programmed ROM from the manufacturer for large series, or a PROM variant which was only programmable once; sometimes this was signified with the designation OTP, standing for “one-time programmable”.

The erasable versions required ceramic packages with quartz windows, making them significantly more expensive than the OTP versions, which could be made dtasheet lower-cost opaque plastic packages. For the erasable variants, quartz was required, instead of less expensive glass, for its transparency to ultraviolet—glass is largely opaque to UV—but the main cost differentiator was the ceramic package itself.

Nowadays microcontrollers are cheap and readily available for hobbyists, with large online communities around certain processors.

On 21 Junethe “world’s smallest computer” was announced by the University of Michigan. The device is a “0. Because they are too small to have conventional radio antennae, they receive and transmit data with visible light. A base station provides light for microcontrolled and programming, and it receives the data.

Over two billion 8-bit microcontrollers were sold in[11] and according to Semico, over four billion 8-bit microcontrollers were sold in A typical home in a developed country is likely to have only four general-purpose microprocessors but around three dozen microcontrollers.

A typical mid-range automobile has about microcintroller microcontrollers. They can also be found in many electrical devices such as washing machines, microwave ovens, and telephones. Historically, the 8-bit segment has dominated the Datashee market [.

The bit MCU market is expected to grow rapidly due to increasing demand for higher levels of precision in embedded-processing systems and the growth in connectivity using the Internet. Cost has plummeted over time, datasheef the cheapest 8-bit microcontrollers being available for under 0. Inthe low-priced microcontrollers above from are all more expensive with inflation calculated between and prices for those specific units at: A microcontroller can be considered a self-contained system with a processor, memory and peripherals and can be used as an embedded system.


While some miceocontroller systems are very sophisticated, many have minimal requirements for memory and program length, with no operating system, and low software complexity. Typical input and output devices include switches, relayssolenoidsLED ‘s, small or custom liquid-crystal displaysradio frequency devices, and sensors for data such as temperature, humidity, light level etc. Microcontrollers must dataaheet real-time predictable, though not necessarily fast response to events in the embedded system they are controlling.

When certain events occur, an interrupt system can signal the processor to suspend processing the current instruction sequence and to begin an interrupt service routine ISR, or “interrupt handler” which will perform any processing required based on the source of the interrupt, before returning to the original instruction sequence. Possible interrupt sources are device dependent, and often include events such as an internal timer overflow, completing an analog to digital conversion, a logic level change on an input such as from a button being pressed, and data received on a communication microclntroller.

Where power consumption is important as in battery devices, interrupts may also wake a microcontroller from a low-power sleep state where the processor is halted until required to do something by a peripheral event. Typically micro-controller programs must fit in the available on-chip memory, since it would be costly to provide a system with external, expandable memory.

Compilers and assemblers are used to convert both high-level and assembly language codes into a compact machine code for storage in the micro-controller’s memory. Depending on the device, the program memory may be permanent, read-only memory that can only be programmed at the factory, or it may microcontroloer field-alterable flash or erasable read-only memory.

Manufacturers have often produced special versions of their microcintroller in order to help datsheet hardware and software development of the target system. Originally these included EPROM versions that have datashdet “window” on the top of the device through which program memory can be erased by ultraviolet light, ready for reprogramming after a programming “burn” and test cycle.

Other versions datasheft be available where the ROM is accessed as an external device rather than as internal memory, however these are becoming rare due to the widespread availability of cheap microcontroller programmers. The use of field-programmable devices on a micro controller may allow field update of the firmware or permit late factory revisions to products that have been assembled but not yet shipped.

Programmable memory also reduces the lead time datashwet for deployment of a new product. Where hundreds of thousands of identical devices are required, using parts programmed at the time of manufacture can be economical.

These ” mask programmed ” parts have the program laid down in the same way as the logic of catasheet chip, at the same time. A customized micro-controller incorporates a block of digital logic that can be personalized for additional processing capability, peripherals and interfaces that are adapted to the requirements of the application. GPIO pins are software configurable to either an input or an output state. When GPIO pins are configured to an input state, they are often used to read sensors or external signals.

Configured to the output state, GPIO pins can drive vatasheet devices such as LEDs or motors, often indirectly, through external power electronics. Many embedded systems need to read sensors that produce analog signals.

Buy online Atmel 89C51 Microcontroller India – Robomart

This is the purpose of the analog-to-digital converter ADC. Since processors are built to interpret and process digital data, i. So the analog to digital converter is used to convert the incoming data into a form that the processor can recognize. A less common feature on some microcontrollers is a digital-to-analog converter DAC that allows the processor to output analog signals or voltage levels. In addition to the converters, many embedded microprocessors include a variety of timers as well.

One of the most common types of timers is the programmable interval timer PIT.

ATMEL 89C51 | AT89C51 Microcontroller Pin Diagram & Description

A PIT may either count down from some value to zero, or up to the capacity of the count register, overflowing to zero. Once it reaches zero, it sends an interrupt to the processor indicating that it has finished counting. This is useful for devices such as thermostats, which periodically test the temperature around them to see if they need to turn the air conditioner on, the heater on, etc.


A dedicated pulse-width modulation PWM block makes it possible for the CPU to control power convertersresistive loads, motorsetc. Micro-controllers may not implement an external address or data bus as they integrate RAM and non-volatile memory on the same chip as the CPU. Using fewer pins, the chip can be placed in a much smaller, cheaper package. Integrating the memory and other peripherals on a single chip and testing them as a unit increases the cost of that chip, but often results in decreased net cost of the embedded system as a whole.

Even if the cost of a CPU that has integrated peripherals is slightly more than the cost of a CPU and external peripherals, having fewer chips typically allows a smaller and cheaper circuit board, and reduces the labor required to assemble and test the circuit board, in addition to tending to decrease the defect rate for the finished assembly. A micro-controller is a single integrated circuitcommonly with the following features:.

This integration drastically reduces the number of chips and the amount of wiring and circuit board space that would be needed to produce equivalent systems using separate chips. Furthermore, on low pin count devices in particular, each pin may interface to several internal peripherals, with the pin function selected by software.

This allows a part to be used in a wider variety of applications than if pins had dedicated functions. Micro-controllers have proved to be highly popular in embedded systems since their introduction in the s. Some microcontrollers use a Harvard architecture: Where a Harvard architecture is used, instruction words for the processor may be a different bit size than the length of internal memory and registers; for example: The decision of which peripheral to integrate is often difficult.

The microcontroller vendors often trade operating frequencies and system design flexibility against time-to-market requirements from their customers and overall lower system cost. Manufacturers have to balance the need to minimize the chip size against additional functionality. Microcontroller architectures vary widely. Other designs are purpose built for control applications.

A micro-controller instruction set usually has many instructions intended for bit manipulation bit-wise operations to make control programs more compact.

Microcontrollers traditionally do not have a math coprocessorso floating point arithmetic is performed by software. Microcontrollers were originally programmed only in assembly languagebut various high-level programming languagessuch as CPython and JavaScriptare now also in common use to target microcontrollers and embedded systems.

Some microcontrollers have environments to aid developing certain types of applications. Microcontroller vendors often make tools freely available to make it easier to adopt their hardware. Microcontrollers with specialty hardware may require their own non-standard dialects of C, such as SDCC for thewhich prevent using standard tools such as code libraries or static analysis tools even for code unrelated to hardware features. Interpreters may also contain nonstandard features, such as MicroPythonalthough a fork, CircuitPythonhas looked to move hardware dependencies to libraries and have the language adhere to a more CPython standard.

Interpreter firmware is also available for some microcontrollers.

Typically these interpreters support interactive programming. Simulators are available for some microcontrollers. These allow a developer to analyze what the behavior of the microcontroller and their program should be if they were using the actual part.

A simulator will show the internal processor state and also that of the outputs, as well as allowing input signals to be generated. While on the one hand most simulators will be limited from being unable to simulate much other hardware in a system, they can exercise conditions that may otherwise be hard to reproduce at will in the physical implementation, and can be the quickest way to debug and analyze problems.

Recent microcontrollers are often integrated with on-chip debug circuitry that when accessed by an in-circuit emulator ICE via JTAGallow debugging of the firmware with a debugger.

As of [update]there are several dozen microcontroller architectures and vendors including:. Many others exist, some of which are used in very narrow range of applications or are more like applications processors than microcontrollers.

The microcontroller market is extremely fragmented, with numerous vendors, technologies, and markets. Note that many vendors sell or have sold multiple architectures.