ROHINI COLLEGE OF ENGINEERING & TECHNOLOGY
4.1 ARCHITECTURE OF 8051
MICROCONTROLLER EVOLUTION
First, microcontrollers were developed in the mid-1970s. These were basically
calculator- based processors with small ROM program memories, very limited RAM
data memories and a handful of input/output ports.
As silicon technology developed, more powerful, 8-bit microcontrollers were
produced. In addition to their improved instruction sets, these microcontrollers
included on-chip counter/timers, interrupt facilities, and improved I/O handling.
On-chip memory capacity was still small and was not adequate for many applications.
One of the most significant developments at this time was the availability of on-chip
ultraviolet erasable EPROM memory. This simplified the product development time
considerably and for the first time, also allowed the use of microcontrollers in low-
volume applications.
The 8051 family was introduced in the early 1980s by Intel. Since its
introduction, the 8051 has been one of the most popular microcontrollers and has
been second- sourced by many manufacturers. The 8051 currently has many different
versions and some types include on-chip analogue-to-digital converters, a
considerably large size of program and data memories.
INTRODUCTION TO 8051:
The Intel MCS-51 (commonly referred to as 8051) is a Harvard architecture,
single chip microcontroller (μC) series which was developed by Intel in 1980 for use in
embedded systems. The 8051 architecture provides many functions (CPU, RAM, ROM,
I/O, interrupt logic, timer,etc.) in a single package
Features of 8051:
8-bit ALU, Accumulator, 8-bit Registers and 8-bit data bus; hence it is
an 8-bit microcontroller
16-bit program counter
8-bit Processor Status Word(PSW)
8-bit Stack Pointer
EC8691 MICROPROCESSORS AND MICROCONTROLLERS
, ROHINI COLLEGE OF ENGINEERING & TECHNOLOGY
Internal RAM of128bytes
On chip ROM is4KB
Special Function Registers (SFRs) of 128bytes
32 I/O pins arranged as four 8-bit ports (P0 -P3)
Two 16-bit timer/counters : T0 andT1
Two external and three internal vectored interrupts
Full duplex UART (serialport)
BLOCK DIAGRAM
Figure 4.1.1 8051 Microcontroller Block Diagram
[Source: “The 8051Microcontroller and Embedded Systems: Using Assembly and C” by Mohamed Ali
Mazidi, Janice Gillispie Mazidi, Rolin McKinlay , pg.no.29]
EC8691 MICROPROCESSORS AND MICROCONTROLLERS
4.1 ARCHITECTURE OF 8051
MICROCONTROLLER EVOLUTION
First, microcontrollers were developed in the mid-1970s. These were basically
calculator- based processors with small ROM program memories, very limited RAM
data memories and a handful of input/output ports.
As silicon technology developed, more powerful, 8-bit microcontrollers were
produced. In addition to their improved instruction sets, these microcontrollers
included on-chip counter/timers, interrupt facilities, and improved I/O handling.
On-chip memory capacity was still small and was not adequate for many applications.
One of the most significant developments at this time was the availability of on-chip
ultraviolet erasable EPROM memory. This simplified the product development time
considerably and for the first time, also allowed the use of microcontrollers in low-
volume applications.
The 8051 family was introduced in the early 1980s by Intel. Since its
introduction, the 8051 has been one of the most popular microcontrollers and has
been second- sourced by many manufacturers. The 8051 currently has many different
versions and some types include on-chip analogue-to-digital converters, a
considerably large size of program and data memories.
INTRODUCTION TO 8051:
The Intel MCS-51 (commonly referred to as 8051) is a Harvard architecture,
single chip microcontroller (μC) series which was developed by Intel in 1980 for use in
embedded systems. The 8051 architecture provides many functions (CPU, RAM, ROM,
I/O, interrupt logic, timer,etc.) in a single package
Features of 8051:
8-bit ALU, Accumulator, 8-bit Registers and 8-bit data bus; hence it is
an 8-bit microcontroller
16-bit program counter
8-bit Processor Status Word(PSW)
8-bit Stack Pointer
EC8691 MICROPROCESSORS AND MICROCONTROLLERS
, ROHINI COLLEGE OF ENGINEERING & TECHNOLOGY
Internal RAM of128bytes
On chip ROM is4KB
Special Function Registers (SFRs) of 128bytes
32 I/O pins arranged as four 8-bit ports (P0 -P3)
Two 16-bit timer/counters : T0 andT1
Two external and three internal vectored interrupts
Full duplex UART (serialport)
BLOCK DIAGRAM
Figure 4.1.1 8051 Microcontroller Block Diagram
[Source: “The 8051Microcontroller and Embedded Systems: Using Assembly and C” by Mohamed Ali
Mazidi, Janice Gillispie Mazidi, Rolin McKinlay , pg.no.29]
EC8691 MICROPROCESSORS AND MICROCONTROLLERS
