Embedded system custom single purpose processors

Alpha Breathing : (2 Mins)

The three steps for alpha breathing are

• Breathe in

• Breathe out

• Hold

(Repeat the three steps for 8 times)

Chapter 4 Custom Single Purpose Processors

Processor

• Digital circuit that performs a computation tasks

• Controller and datapath

• General-purpose: variety of computation tasks

• Single-purpose: one particular computation task

• Custom single-purpose: non-standard task

• A custom single-purpose processor may be

– Fast, small, low power

– But, high NRE, longer time-to-market, less flexible

•  

Digital Camera

CMOS transistor on silicon

• Transistor

– The basic electrical component in digital systems

– Acts as an on/off switch

– Voltage at “gate” controls whether current flows from source to drain

– Don’t confuse this “gate” with a logic gate

CMOS transistor implementations

• Complementary Metal Oxide Semiconductor

• We refer to logic levels

– Typically 0 is 0V, 1 is 5V

• Two basic CMOS types

– nMOS conducts if gate=1

– pMOS conducts if gate=0

– Hence “complementary”

• Basic gates

– Inverter, NAND, NOR

Basic gates

Basic logic gates

Combinational Logic Design

Combinational Circuit

• A combinational circuit is a digital circuit whose output is purely a function of its current inputs;

• such a circuit has no memory of past inputs.

Sequential Logic Design

Design task

• Define system functionality

• Convert functionality to physical implementation while

• Satisfying constrained metrics

• Optimizing other design metrics

• Designing embedded systems is hard

• Complex functionality

• Millions of possible environment scenarios

• Given this implementation model

– Sequential logic design quickly reduces to combinational logic design

Improving Productivity

Brain Activation: (2 mins)

Survey and Reading by students (18 mins.)

Survey:

Define custom single purpose processors.

Mention the components of combinational logic.

Mention the components of sequential logic.

List out the steps involved in creating a data path.

List out the steps in creating a controller.

Reading:

1. What are the steps in creating FSM?

2. List out the basic logic gates?

Guided Reading with hints

Page No.: 68-74

Discussion (9 mins.)

Reconstruct – Mind map (7 mins.)

Summary (5 mins.)

• Custom single-purpose processors– Combinational logic– Sequential logic

• Sequential components• Creating data path and controller • FSM

– Hardware• Processor • CMOS transistor on silicon

• Straightforward design techniques• Can be built to execute algorithms• Typically start with FSMD• Optimizing Single purpose processors• CAD tools can be of great assistance

Gazing/Rote memory: (2 mins)

• Combinational logic

• Combinational logic components

• Sequential logic

• Sequential logic components

• Custom single-purpose processor design

• RT-level custom single-purpose processor design

Assessment (MCQ And higher orderquestions)

1. Basic logic gates _________.

(a) NAND

(b) NOR

(c) NOT

(d) EXNOR

2. Drivers ,Inverters are __________ .

(a) OR and XOR

(b) AND and NOT

(c) XOR and XNOR

(d) OR and AND

3. CMOS stands for ___________ .

(a) Complementary Metal Oxide Semiconductor

(b) Complementary Metal Oxide Stub

(c) Complementary Metal Oxide Semi transistor

(d) None

4. A multiplexer is sometimes called as

. (a) selector

(b) distributor

(c) transistor

(d) collector

5. The components of combinational logic is ______________

.

(a) Multiplexer

(b) Decoder

(c) ALU

(d) All the above

Two mark Questions:

State the benefits of custom single purpose processors.

Mention some of the combinational logic gates.

Define combinational logic design.

Mention the advantages and disadvantages in CMOS transistors.

Define the performance metric for throughput and time in embedded system.

[C] Descriptive Questions:

Explain combinational logic.

Differentiate the features of pMOs, CMOS and nMOS transistors.