74147 datasheet specifies that this IC is a TTL encoder feature priority decoding of the inputs to ensure that only the highest-order data line is encoded. The decimal zero condition requires no input condition because zero is encoded when all 9 data lines are at a high logic level.

Pin Description:

Pin

Symbol

Description

1

A3

decimal data input (active low)

2

A4

decimal data input (active low)

3

A5

decimal data input (active low)

  4

A6

decimal data input (active low)

5

A7

decimal data input (active low)

6

Y2

BCD address output (active low)

7

Y1

BCD address output (active low)

8

GND

ground

9

Y0

BCD address output (active low)

10

A8

decimal data input (active low)

11

A0

decimal data input (active low)

12

A1

decimal data input (active low)

13

A2

decimal data input (active low)

14

Y3

BCD address output (active low)

15

NC

no connection

16

Vcc

supply voltage