The enhancement on a simple encoder circuit, in terms of handling all possible input combinations has lead to the development of special circuits known as Priority Encoders. These circuits facilitate in compressing several inputs into numerous small outputs. The quality feature of these encoders is encoding the inputs just to make sure that only highest order lines are encoded. The result or output of the priority encoder should be a binary representation of ordinal numbers articulated in BCD format. In addition, these also manage interrupt requests through high priority request. Whenever there is more than one active input at same time, then highest priority input will be given more preference. One can find priority encoders in standard or normal IC form such as TTL 74LS147 or TTL 74LS148. Basically, the former encodes 9 datelines to 4 lines as in (8-4-2-1) BCD. And the latter expresses 8 datelines to 3 lines as in 4-2-1 (octal) binary. In order to provide octal expansion with no requirement of external circuitry, one needs Cascading Circuitry. Data inputs and data outputs are active even at low levels. Priority encoders find wide range of applications as in keyboard encoding, range selection, Bit level encoding, code converters and generators.

1. Full Custom Digital IC
Design of Priority
Encoder 74LS 147 & 148
Team members
Bhargav-l401
Srikanth-452
Venkatesh-459
Vishesh Thakur Singh-460

2.  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

3. 4 to 2 encoder

4.  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.

5. 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

6. 8 to 3 priority encoder

7. Functional Block Diagram of 74LS148
• Output A0=∑(1,3,5,7)
• Output A1=∑(2,3,6,7)
• Output A2=∑(4,5,6,7)

8. 10 to 4 priority encoder
10 X 4
Priority
Encoder
Lowest priority
Highest priority
D0
D9
Y0
Y1
Y2
Y3

9. Functional Block Diagram of 74LS147

10. 8 X 3 Priority Encoder
Schematic View Symbol view

11. Verifying Functionality of 74LS147

12. Schematic view of 10 X 4 Priority encoder

13. Symbol of 74LS147

14. Functional Verification of 74LS148

15. Layout of
74LS148

16. Layout of
74LS147

17. Applications
 Keyboard Encoder
 Interrupt Requests
 Positional Encoders

18. Priority Encoder Navigation

19. Targets achieved
S.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

20. Future Scope
• 16-to-4 Priority
Encoder:-
 As many as 16 interrupts
can be serviced based upon
their priority

21. Thank You