INTRODUCTION TO
MICROCONTROLLER
What is a Microcontroller
• A microcontroller is a complete microprocessor system, consisting
of microprocessor, limited amount of ROM or EPROM, RAM & I/O
ports all built on a single integrated circuit.
• Microcontroller can be used to perform control functions so it is
comparable with a microcomputer.
• It must include full or nearly full implementation of a standard
microprocessor, ROM or EPROM, RAM, parallel I/O ports, serial
ports, timer, clock.
• More complex than a microprocessor.
Advantages of Microcontroller over Microprocessor
• Cost of microcontroller is less than microprocessor based system
• Microcontroller has more I/O components than microprocessor
based system.
• Unlike microprocessors Microcontrollers can be used in wide variety
of intelligent products like personal computers keyboards or can be
used in devices with artificial intelligence.
• Many low cost products like toys, washing machines, microwave
ovens, electric drills etc are based on microcontrollers & not on
microprocessor based system
Features of Microcontroller 8051
• 8051 microcontroller has an 8-bit ALU.
• 4 KB (4K x 8 bit) ROM EPROM
• 128 byte (128 x 8 bit) RAM
• Dual 16-bit timer, event counter.
• 32 I/O lines for four 8- bit I/O ports.
• Full featured serial port.
• It can address 64 KB of program memory
• It can address 64 KB of data memory
• Powerful instruction set with 111 instructions.
• Two external interrupt.
• Clock upto 12-MHz frequency.
Memory mapping of Microcontroller 8051
Memory mapping of Microcontroller 8051
Program Memory
Data Memory
Read-Only Memory (ROM) space
Random Access Memory (RAM)
space
Used for storing programs &
variable data
Used for general read/write data
storage
Instruction fetches are taken from
program memory space.
It is a read/write memory space
Processor can read instruction from
this space, but cannot write the data
into this memory. It reads
instructions to be executed from
this memory space.
Processor can read data from this
memory space & can write data to
this memory space. It cannot
execute instructions from this
memory space.
It has internal ROM(EPROM)
It has internal RAM 128 bytes.
4 Kbytes program memory can be
expanded by additional 60Kbytes,
making it 64KB program memory.
& 22 special function registers
.memory can be expanded by
additional 60Kbytes, making it
64Kbytes data memory.
Microcontroller 8051 family
8048, 8049, 8050
• 8048 was Intel’s 1st microcontroller. All 8048, 8049, 8050 have same
architecture except memory size.
• The memory size doubles in each case.8048 supports 1Kbytes of internal
memory (ROM). 8049 supports 2Kbytes of internal ROM & 8050
supports 4Kbytes of internal ROM.
• 8048 has 64 bytes internal RAM, including 32 bytes of register memory.
8049 & 8050 have a total of 128 & 256 bytes of RAM respectively.
• 27 I/O lines. 8-bit timer event counter.
• Low cost & hence very popular.
8052
• 8052 is a simple expansion of 8051.
• 8Kbytes of onboard ROM & 256 Kbytes onboard RAM.
• Allows programmer to write larger programs that can use more data.
• Cost of 8052 is more than 8051.
• Has one extra 16-bit counter-timer which gives more flexibility.
Microcontroller 8051 family
8031, 8032
• 8031 is alternative version of 8051 & 8032 is alternative version of
8052.
• They do not have onboard ROM. They may use external ROM for
program memory.
• Excellent devices for prototyping & low volume products.
8052 AH-BASIC
• 8052 AH-BASIC is another form of 8052.
• Programmer can use BASIC for writing instructions rather than using
assembly language.
Compare between 8051 & 8052
8051
8052
4Kbytes of onboard ROM or EPROM
8Kbytes of onboard ROM or EPROM
128 bytes of onboard RAM
256 bytes of onboard RAM
Has a dual 16-bit timer event counter Has an extra 16-bit timer event
counter
Cost is less
Cost is more
Used in high volume applications &
allows to write large programs
Used in high volume applications &
allows to write large programs, larger
than in 8051
Applications of Microcontroller
• Microcontroller is a single chip microcomputer.
• They are used as independent controllers in machines or as slaves in
distributed processing.
• They are used as machine tools, chemical processors, medical
instrumentation & sophisticated guidance control.
• Many low cost products such as toys, microwave oven etc are based on
microcontroller.
• The personal computer keyboards are implemented with microcontroller.
It replaces scanning, debounce, matrix decoding & serial transmission
circuits.