Home | | Microprocessors and Microcontrollers | Architecture of 8051 Micro Controller

Chapter: Microprocessor and Microcontroller : 8051 Micro Controller

Architecture of 8051 Micro Controller

1 Memory Organization 2 Interrupt Structure 3 Port Structure 4 Timer/Counter


Architecture of 8051



1 Memory Organization


ü Logical separation of program and data memory

ü Separate address spaces for Program (ROM) and Data (RAM) Memory


ü Allow Data Memory to be accessed by 8-bit addresses quickly and manipulated by 8-bit CPU


Program Memory


ü Only be read, not written to

ü The address space is 16-bit, so maximum of 64K bytes


ü Up to 4K bytes can be on-chip (internal) of 8051 core

ü PSEN (Program Store Enable) is used for access to external Program Memory


Data Memory


ü Includes 128 bytes of on-chip Data Memory which are more easily accessible directly by its instructions


ü There is also a number of Special Function Registers (SFRs)


ü Internal Data Memory contains four banks of eight registers and a special 32- byte long segment which is bit addressable by 8051 bit-instructions

ü External memory of maximum 64K bytes is accessible by “movx”




2 Interrupt Structure


ü The 8051 provides 4 interrupt sources

ü Two external interrupts

ü Two timer interrupts


3 Port Structure


ü The 8051 contains four I/O ports

ü All four ports are bidirectional


ü Each port has SFR (Special Function Registers P0 through P3) which works like a latch, an output driver and an input buffer


ü Both output driver and input buffer of Port 0 and output driver of Port 2 are used for accessing external memory


ü Accessing external memory works like this


ü Port 0 outputs the low byte of external memory address (which is time- multiplexed with the byte being written or read)


ü Port 2 outputs the high byte (only needed when the address is 16 bits wide)

ü Port 3 pins are multifunctional

ü     The alternate functions are activated with the 1 written in the corresponding bit in the port SFR


Table 4.1 Alternate Functions of Port 3 pins



4 Timer/Counter


ü The 8051 has two 16-bit Timer/Counter registers

1.     Timer 0


2.     Timer 1

ü Both can work either as timers or event counters

ü Both have four different operating modes

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail
Microprocessor and Microcontroller : 8051 Micro Controller : Architecture of 8051 Micro Controller |

Privacy Policy, Terms and Conditions, DMCA Policy and Compliant

Copyright © 2018-2023 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.