MICROCONTROLLER 8051 ARCHITECTURE

It is 8-bit microcontroller, means MC 8051 can Read, Write and Process 8 bit data. This is mostly used microcontroller in the robotics, home appliances like mp3 player, washing machines, electronic iron and industries. Mostly used blocks in the architecture of 8051 are as follows:

128 Byte RAM for Data Storage

MC 8051 has 128 byte Random Access memory for data storage. Random access memory is non volatile memory. During execution for storing the data the RAM is used. RAM consists of the register banks, stack for temporary data storage. It also consists of some special function register (SFR) which are used for some specific purpose like timer, input output ports etc. Normally microcontroller has 256 byte RAM in which 128 byte is used for user space which is normally Register banks and stack. But other 128 byte RAM which consists of SFRs. We will discuss the RAM in detail in next section.

Now what is the meaning of 128 byte RAM. What are address range which is provided for data storage. We will discuss here. We know that 128 byte = 2⁷ byte.

Since 2⁷ bytes so last 7 bits can be changed so total locations are from 00H to 7F H. This procedure of calculating the memory address is called as “memory mapping”. We can save data on memory locations from 00H to 7FH. Means total 128 byte space from 00H to 7FH is provided for data storage.

 4KB ROM

In 8051, 4KB read only memory (ROM) is available for program storage.This is used for permanent data storage. Or the data which is not changed during the processing like the program or algorithm for specific applications.

This is volatile memory; the data saved in this memory does not disappearafter power failure.

We can interface up to 64KB ROM memory externally if the application islarge. These sizes are specified different by their companies.

Address Range of PC: Address range of PC means program counter (which points the next instruction to be executing) can be moved between these locations or we can save the program from this location to this location.

Difference between RAM and ROM

RAM is used for data storage while ROM is used for program storage.

Data of RAM can be changed during processing while data of ROM can’tbe changed during processing.

We can take an example of calculator. If we want to perform addition oftwo numbers then we type the two numbers in calculator, this is saved in the RAM, but the Algorithms by which the calculation is performed is saved in the ROM. Data which is given by us to calculator can be changed but the algorithm or program by which calculation is performed can’t be changed.