Full Custom Digital IC Design of Priority Encoder 74LS 147 & 148

Team members

Bhargav-l401 Srikanth-452

Venkatesh-459 Vishesh Thakur Singh-460

What is an “Encoder”

• An encoder is a device or a combinational circuit that converts information from one format or code to another.

•  Digital Encoder are more commonly called a Binary Encoder takes all its data inputs one at a time and then converts them into a single encoded output. 

• An "n-bit" binary encoder has 2n input lines and n-bit output lines 

4 to 2 encoder

Priority Encoder:

•A  priority encoder is a special type of encoder whose output corresponds to the currently active input which has the highest priority. So when an input with a higher priority is present, all other inputs with a lower priority will be ignored.

Types of Priority Encoders(a) IC SN54/74 LS147

(b) IC SN54/74 LS148

• 8-to-3 bit priority encoder • 10-to-4 bit priority encoder

8 to 3 priority encoder

Functional Block Diagram of 74LS148

• Output A0=∑(1,3,5,7)

• Output A1=∑(2,3,6,7)

• Output A2=∑(4,5,6,7)

10 to 4 priority encoder

10 X 4

Priority Encoder

Lowest priority

Highest priority

D0

D9

Y0

Y1

Y2

Y3

Functional Block Diagram of 74LS147

8 X 3 Priority EncoderSchematic View Symbol view

Verifying Functionality of 74LS147

Schematic view of 10 X 4 Priority encoder

Symbol of 74LS147

Functional Verification of 74LS148

Layout of 74LS148

Layout of 74LS147

Applications

Keyboard Encoder

Interrupt Requests

Positional Encoders

Priority Encoder Navigation

Targets achievedS.No: Specifications: Value(74LS148) Value(74LS147

)1. Technology 180nm 180nm

2. Supply (Vdd) 1.8v 1.8v

3. Area 62.26 um. x 283.15 um.

76.97 um. x 279.2 um

4. Power without Parasitics(w)

5.69809658e-07 -1.0852728e-05

5. Power with Parasitics(w)

2.1360425e-06 -8.6488442e-07

Future Scope

•16-to-4 Priority Encoder:-

As many as 16 interrupts can be serviced based upon their priority

Thank You