The last decade has seen an exciting revolution in the capabilities of microprocessor.Manufacturers have produced 16- & 32- bit processors to answer the needs for even 4 more powerful CPU processing capabilities.
Because of their processing power & speed, these processors have found their way into the design of stand-alone products. Microcontroller is another branch in the evolution of microprocessor capability.
It is a branch, which manufacturers have been developing with equal vigor. Instead of focusing upon larger word widths & address space, the emphasis here has been upon exceedingly fast real-time control. It has focused upon the integration of the facilities needed to support fast control into a single chip.
In the past, the highest performance real -time control applications have employed microprocessors with interrupt handler chips, programmable timer chips and ROM and RAM chips to achieve what can now be achieved in a single state-of-the-art microcontroller chip.
Its on chip resources provide an integrated approach to a variety of real-time control tasks. By operating the chip in the expanded mode, not only do we gain on-chip features, but also we can augment these features as we see fit. All the power available in any peripheral chip becomes available to our designs
based upon such a microcontroller chip.
The MCS51 architecture consists, of the following features:
o Eight-bit CPU with registers A(accumulator and B
o Sixteen-bit program counter(PC) and data pointer(DPTR)
o Eight-bit program status word(PSW)
o Eight-bit stack pointer(SP)
o Internal ROM(8051) or EPROM(8751) or EEPROM(8951)
o Internal RAM of 128 bytes:
0 Four register banks each containing eight registers
0 Sixteen bytes, which may be addressed at the bit level