You might have been using the 8051 microcontroller for a long time now, or you might be new to it. These microcontrollers are versatile integrated circuits with many capabilities.
But, why is the 8051 called an 8-bit microcontroller? The 8051 is called an 8-bit microcontroller because it processes 8 bits of data every machine cycle. All assembly instructions happen 8-bits at a time. Also, all internal registers are 8-bit in size and all read and write operations happen 8-bits at a time.
What does 8-bit mean?
Understanding the basics of what 8-bit means, will give you a better understanding of the question of why the 8051 is called an 8-bit microcontroller.
Before the digital age, all electronics were analog. It dealt with a continuous range of voltages.
In the world of microcontrollers, all data, memory, program code is digital (0’s and 1’s).
A single bit is either a 0 or 1.
A collection of eight 0’s and/or 1’s is known as 8-bits (or a byte).
A deeper look at why the 8051 is called an 8-bit microcontroller
A 8051 microcontroller has registers, address buses and data buses.
A register is one of the main components of a microcontroller whose primary use is to store data.
Registers have read/ write operations which means that you can either just read the contents of the register, or write new data to it.
To move information to these registers, microcontrollers require data or address buses. They provide a means of moving information from one place to another.
Think of them as highways.
As we saw above, all data is either a 0 or 1.
The registers in an 8051 microcontroller store data that is 8-bits in length.
Also, the address and data buses move data that is 8-bits in length which is the main reason why the 8051 is called an 8-bit microcontroller.
Different types of 8-bit registers in the 8051
The 8051 has different types of 8-bit registers, each used for certain applications.
The registers are General Purpose and Special Function. It has a total of 256 bytes of RAM in total of which 128 bytes are used for the General Purpose Registers, and 128 bytes for the Special Function Register.
Were the earlier versions of the 8051 microcontroller 8-bit?
Intel Corporation are the developers of the 8051 microcontroller.
However, they weren’t the first microcontrollers they developed.
The first microcontrollers developed by Intel was the 4004. A 4-bit microcontroller.
This meant that it had registers, data buses and address busses that were 4-bit in size.
Therefore it was considered a 4-bit microcontroller.
Are the 8051 microcontroller peripherals 8-bit?
Peripherals are certain parts of a microcontroller that have specific functionalities that help a microcontroller achieve a certain task.
Microcontroller peripherals include things like Timers, Analog to Digital Converters, Pulse Width Modulation, General Purpose Input/Outputs and Serial Communication.
A 8051 microcontroller has two dedicated 16-bit timers, Serial communication (UART) and General Purpose Input/Outputs.
But, isn’t the 8051 microcontroller 8-bit? How can it have 16-bit timers?
Yes it still is an 8-bit microcontroller, the timer values are just stored in two 8-bit registers, and their total value of the timer is a combination of these two registers.
The lower byte is stored in register ‘TL’, and the higher byte is stored in register ‘TH’.
Are all 8051 microcontrollers 8-bit?
The 8051 microcontroller has different versions available that vary in things like ROM, RAM, number of timers, and interrupt sources.
The two versions are the 8052, and the 8031.
Below is a table of their comparisons:
| Feature | 8051 | 8052 | 8031 |
| ROM(bytes) | 4K | 8K | 0K |
| RAM(bytes) | 128 | 256 | 128 |
| Timers | 2 | 3 | 2 |
| I/O pins | 32 | 32 | 32 |
| Serial port | 1 | 1 | 1 |
| Interrupt sources | 6 | 8 | 6 |
Both these versions, just like the 8051, are 8-bit microcontrollers.
At this moment in time, all three versions of the microcontroller are only available as 8-bit microcontrollers.
How do you know if a microcontroller is 8-bit?
Many if not most electronic devices come with a user manual.
This user manual helps us learn how to use the device. It tells us what each button does, and what functions the device has.
Lucky enough for you and me, manufacturers of microcontrollers have written up a user manual for each device.
This user manual is commonly known as a datasheet.
It lets us know all the features of a microcontroller, what each pin does, how to use it etc.
The datasheet also contains information of whether a microcontroller is an 8-bit, 16-bit or 32-bit microcontroller.
So, if you need to find information about your microcontroller, just consult its datasheet which is available online.
Is the 8-bit 8051 microcontroller a good for you?
Microcontrollers have come a long way from their humble 4-bit days.
You now have the option of 8-bit, 16-bit and 32-bit microcontrollers.
The choice of which of these microcontrollers to choose all comes down to the needs of your application. If you require higher computation power, the 32-bit microcontroller is your best option.
However, if lower power consumption is a necessity, the 8-bit microcontroller is your best bet.
Below are some of the advantages of using an 8-bit microcontroller like the 8051.
Cheap and easy to use
An 8-bit microcontroller is a great choice for the beginner, or when money is an issue.
8-bit microcontrollers are cheaper and easier to use compared to their counterparts.
If you are a beginner just getting started 8-bit microcontrollers are your best friend, as its architecture is simpler and has a programming model that is easier to understand.
Also, most of the time it requires a single supply which lowers costs, and if funds are an issue, is again your best friend.
Lower power
Power is a precious commodity in many areas in life.
It helps run our homes, workplaces and is needed by every electronic device.
But, power is not an abundant source.
So, when designing embedded systems, a lot of thought has to go into how much power microcontrollers consume.
The less the better!
8-bit microcontrollers use less power, which is a great advantage when it comes to designing an embedded system.
Package style of 8051 microcontroller
The 8051 microcontroller is available in two package styles which provide different mounting styles.They include the TQFP and PDIP.
The TQFP package style is 44 pin surface mount integrated circuit and the PDIP is a 40 pin through hole integrated circuit.
If you are just prototyping, or building a one off project, the PDIP package will suit your application.
If you are creating a final version of your product, or mass producing circuits, the TQFP style of package is a great choice.
Other types of 8-bit microcontroller
Is the 8051 the only 8-bit microcontroller available?
No, there are a plethora of 8-bit microcontrollers available for you to pick and choose. The 8051 is just one of many.
There are a number of different manufacturers that develop microcontrollers. The top companies that develop the bulk of microcontrollers used in the market today include:
- ATMEL (now owned by microchip)
- MICROCHIP
- NXP
- TEXAS INSTRUMENTS
These companies all develop different ranges of microcontrollers that vary in specifications.
But, what is common is they all have a range of 8-bit microcontrollers.
What is the difference between 8-bit, 16-bit, and 32-bit microcontrollers?
So, an 8051 is called an 8-bit microcontroller because it processes data 8-bits every machine cycle. It has registers, data and address buses all capable of storing and transferring this data 8-bits at a time.
While a 8-bit microcontroller processes 8 bits of data a time, a 16-bit microcontroller processes 16 bits and a 32-bit microcontroller processes 32 bits.
The main difference between the three is how many bits are processed every machine cycle.
The 16-bit and 32-bit microcontrollers have the benefits of faster operation, and better precision. The downside however, is that they consume more power.
