MICROCONTROLLERS
AND
EMBEDDED
PROCESSORS
x86 PC
Embedded
Applications
􀂉 Many manufactures of general-purpose
microprocessors have targeted their
microprocessor for the high end of the
embedded market
􀂾 There are times that a microcontroller is
inadequate for the task
􀂉 When a company targets a generalpurpose
microprocessor for the
embedded market, it optimizes the
processor used for embedded systems
􀂉 Very often the terms embedded
processor and microcontroller are used
interchangeably

MICROCONTROLLERS
AND
EMBEDDED
PROCESSORS
x86 PC
Embedded
Applications
(cont’)
􀂉 One of the most critical needs of an
embedded system is to decrease
power consumption and space
􀂉 In high-performance embedded
processors, the trend is to integrate
more functions on the CPU chip and let
designer decide which features he/she
wants to use
􀂉 In many cases using x86 PCs for the
high-end embedded applications
􀂾 Saves money and shortens development
time
􀂃 A vast library of software already written
􀂃 Windows is a widely used and well understood
platform

MICROCONTROLLERS
AND
EMBEDDED
PROCESSORS
Choosing a
Microcontroller
􀂉 8-bit microcontrollers
􀂾 Motorola’s 6811
􀂾 Intel’s 8051
􀂾 Zilog’s Z8
􀂾 Microchip’s PIC
􀂉 There are also 16-bit and 32-bit
microcontrollers made by various chip
makers

MICROCONTROLLERS
AND
EMBEDDED
PROCESSORS
Criteria for
Choosing a
Microcontroller
􀂉 Meeting the computing needs of the
task at hand efficiently and cost
effectively
􀂾 Speed
􀂾 Packaging
􀂾 Power consumption
􀂾 The amount of RAM and ROM on chip
􀂾 The number of I/O pins and the timer on
chip
􀂾 How easy to upgrade to higherperformance
or lower power-consumption
versions
􀂾 Cost per unit

MICROCONTROLLERS
AND
EMBEDDED
PROCESSORS
Criteria for
Choosing a
Microcontroller
(cont’)
􀂉 Availability of software development
tools, such as compilers, assemblers,
and debuggers
􀂉 Wide availability and reliable sources
of the microcontroller
􀂾 The 8051 family has the largest number of
diversified (multiple source) suppliers
􀂃 Intel (original)
􀂃 Atmel
􀂃 Philips/Signetics
􀂃 AMD
􀂃 Infineon (formerly Siemens)
􀂃 Matra
􀂃 Dallas Semiconductor/Maxim

OVERVIEW OF
8051 FAMILY
8051
Microcontroller
􀂉 Intel introduced 8051, referred as MCS-
51, in 1981
􀂾 The 8051 is an 8-bit processor
􀂃 The CPU can work on only 8 bits of data at a
time
􀂾 The 8051 had
􀂃 128 bytes of RAM
􀂃 4K bytes of on-chip ROM
􀂃 Two timers
􀂃 One serial port
􀂃 Four I/O ports, each 8 bits wide
􀂃 6 interrupt sources
􀂉 The 8051 became widely popular after
allowing other manufactures to make
and market any flavor of the 8051, but
remaining code-compatible

OVERVIEW OF
8051 FAMILY
8051
Microcontroller
(cont’)
Interrupt
Control
Bus
Control
CPU
OSC I/O
Ports
Serial
Port
Etc.
Timer 0
Timer 1
On-chip
RAM
On-chip
ROM
for code
P0 P1 P2 P3
Address/Data
TXD RXD
Counter Inputs
External
Interrupts

OVERVIEW OF
8051 FAMILY
8051 Family
􀂉 The 8051 is a subset of the 8052
􀂉 The 8031 is a ROM-less 8051
􀂾 Add external ROM to it
􀂾 You lose two ports, and leave only 2 ports
for I/O operations
Interrupt sources 6 8 6
Serial port 1 1 1
I/O pins 32 32 32
Timers 2 3 2
RAM (bytes) 128 256 128
ROM (on-chip program 4K 8K 0K
space in bytes)
Feature 8051 8052 8031