Introducing Embedded Systems and the Microcontrollers

Introducing Embedded
Systems and the
Microcontrollers
Ravikumar Tiwari
Assistant Professor
Dept. of Electronics,
G.H. Raisoni College of Engineering(Autonomous),Nagpur
ravikumar.tiwari@raisoni.net

System Definition
R.K.Tiwari(ravikumar.tiwari@raisoni.net)
 A way of working, organizing or
performing one or many tasks according to
a fixed set of rules, program or plan.

System Definition
• Also an arrangement in which all units
assemble and work together
according to a program or plan.

Examples of Systems
 Time display system – A watch
 Automatic cloth washing system – A
washing machine

Embedded System
Definitions:
 1. “An embedded system is a system
that has software embedded into
computer-hardware, which makes a
system dedicated for an application (s)
or specific part of an application or
product or part of a larger system.” –
Rajkamal

Embedded System
Definitions:
 2. “An embedded system is one
that has a dedicated purpose
software embedded in a computer
hardware.” –Rajkamal

Embedded System
Definitions:
 3. “It is a dedicated computer
based system for an
application(s) or product. It may
be an independent system or a
part of large system. Its software
usually embeds into a ROM
(Read Only Memory) or flash.” –
Rajkamal

Embedded System
Definitions:
 “It is any device that includes a
programmable computer but is
not itself intended to be a general
purpose computer.” – Wayne Wolf

Embedded System
Definitions:
 “Embedded Systems are the
electronic systems that contain a
microprocessor or a
microcontroller, but we do not
think of them as computers– the
computer is hidden or embedded
in the system.” – Todd D. Morton

Let’s consider a Computer
A computer is a system that has the
following or more components.
 A microprocessor
 A large memory comprising the
following two kinds:
 (a) Primary memory
(semiconductor memories - RAM,
ROM and fast accessible caches)

Computer
 (b) Secondary memory [(magnetic
memory located in hard disks,
diskettes and cartridge tapes, optical
memory in CD-ROM or memory stick
(in mobile computer)] using which
different user programs can load into
the primary memory and can be run.
I/O units such as touch screen,
modem, fax cum modem etc.

Computer
 Input units such as keyboard, mouse,
digitizer, scanner, etc.
 Output units like LCD screen, video
monitor, printer, etc.
 Networking units like Ethernet card,
front-end processor-based server, bus
drivers, etc.
 Operating system (OS).
 General purpose user interfaces and
application- software, mostly in
secondary memory

Now consider Embedded system
–Three main embedded components
 1.Embeds hardware to give computer
like functionalities
 2.Embeds main application software
generally into flash or ROM and the
application software performs
concurrently the number of tasks.

Embedded system components
 3.Embeds a real time operating
system
( RTOS), which supervises the
application software tasks running on
the hardware and organizes the
accesses to system resources
according to priorities and timing
constraints of tasks in the system.

Embedded system RTOS
 Enables execution of concurrent
processes or threads or tasks
 Provides a mechanism to let the
processor run each process as per
scheduling and to do context-switch
between the various processes (threads
or tasks)
 RTOS sets the rules during execution of
application processes to enable finishing
of a process within the assigned time
interval and with assigned priority.

Sophisticated Embedded System
Characteristics
 Dedicated functions
 Dedicated complex algorithms
 Dedicated (GUIs) and other user
interfaces for the application

Characteristics-Contd.
 Real time operations— Defines the ways
in which the system works, reacts to the
events and interrupts, schedules the
system functioning in real time and
executes by following a plan to control
the latencies and to meet the deadlines.
[Latency — Waiting interval between the
instance at which a need to run the
codes arises for task (or interrupt service
routine) following an event and instance
of start executing the codes]

Characteristics-Contd.
 Multi-rate operations — Different
operations may take place at distinct
rates. For example, the audio, video,
network data or stream and events
have the different rates and time
constraints to finish associated
processes.

Constraints of an Embedded
System Design
 Available system-memory
 Available processor speed
 Limited power dissipation when
running the system continuously in
cycles of the system start, wait for
event, wake-up and run, sleep and
stop.

System design constraints
 Performance,
 power,
 size,
 non-recurring design cost, and
 manufacturing costs.

RISC
 RISC, or Reduced Instruction Set
Computer. is a type of microprocessor
architecture that utilizes a small,
highly-optimized set of instructions,
rather than a more specialized set of
instructions often found in other types
of architectures.

Design Feature that
Characterizes RISC
 one cycle execution time: RISC
processors have a CPI (clock per
instruction) of one cycle. This is due to
the optimization of each instruction on
the CPU and a technique called
pipelining.
 pipelining: a techique that allows for
simultaneous execution of parts, or
stages, of instructions to more
efficiently process instructions

Design Feature that
Characterizes RISC
 large number of registers: the RISC
design philosophy generally
incorporates a larger number of
registers to prevent in large amounts
of interactions with memory

How pipelining Works?
 Pipelining, a standard feature in RISC
processors, is much like an assembly
line
 Because the processor works on
different steps of the instruction at the
same time, more instructions can be
executed in a shorter period of time

 A useful method of demonstrating this
is the laundry analogy.

 Let's say that there are four
loads of dirty laundry that need
to be washed, dried, and folded.
We could put the the first load in
the washer for 30 minutes, dry it
for 40 minutes, and then take 20
minutes to fold the clothes.
Then pick up the second load
and wash, dry, and fold, and
repeat for the third and fourth
loads. Supposing we started at
6 PM and worked as efficiently
as possible, we would still be
doing laundry until midnight.
Source:
http://www.ece.arizona.edu/~ece462/Lec03-
pipe/

 However, a smarter approach to
the problem would be to put the
second load of dirty laundry into
the washer after the first was
already clean and whirling
happily in the dryer. Then, while
the first load was being folded,
the second load would dry, and
a third load could be added to
the pipeline of laundry. Using
this method, the laundry would
be finished by 9:30.
Source:
http://www.ece.arizona.edu/~ece462/Lec03-pipe/
(Source: http://www.inf.fh-
dortmund.de/person/prof/si/risc/intro_to_risc/irt0_index.html)

RISC Pipeline
 A RISC processor pipeline operates in
much the same way, although the
stages in the pipeline are different.
 While different processors have
different numbers of steps, they are
basically variations of these five, used
in the MIPS R3000 processor

RISC Pipeline
 1.fetch instructions from memory
 2.read registers and decode the
instruction
 3.execute the instruction or calculate
an address
 4.access an operand in data memory
 5.write the result into a register

RISC Pipeline
 the length of the pipeline is dependent
on the length of the longest step

Pipeline Development(Methods
of Pipelining)
 Superpipelining refers to dividing the
pipeline into more steps.
 The more pipe stages there are, the
faster the pipeline is because each
stage is then shorter.
 Ideally, a pipeline with five stages
should be five times faster than a non-
pipelined processor (or rather, a
pipeline with one stage).

of Pipelining)
 Examples;
 1.Instruction Fetch (First Half)
 2.Instruction Fetch (Second Half)
 3.Register Fetch
 4.Instruction Execute
 5.Data Cache Access (First Half)
 6.Data Cache Access (Second Half)
 7.Tag Check
 8.Write Back

of Pipelining)
• Superscalar pipelining involves
multiple pipelines in parallel.
• Internal components of the processor
are replicated so it can launch multiple
instructions in some or all of its
pipeline stages

of Pipelining)
 Dynamic pipelines have the capability
to schedule around stalls.
 A dynamic pipeline is divided into
three units: the instruction fetch and
decode unit, five to ten execute or
functional units, and a commit unit.

of Pipelining)
 Dynamic is combination of
Superpipelining & superscalar pipeline

Thank you for you
Attention!!!
Any Question..??

Introducing Embedded Systems and the Microcontrollers

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