Digital Electronics

Dr. McLean

GND

A

BI/

RBO

c

d

e

LT

C

B

f

g

a

b

Vcc

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

7447

7-Segment Display

Decoder

Inputs

Outputs

RBI

D

Inputs

a

g

f

b

c

d

e

Input Binary Coded Decimal: DCBA

Inputs

Outputs

Decimal or

Function

LT

RB

I

D

C

B

A

BI/RBO

a

b

c

d

e

f

g

0

1

1

0

0

0

0

1

ON

ON

ON

ON

ON

ON

OFF

1

1

any

0

0

0

1

1

OFF

ON

ON

OFF

OFF

OFF

OFF

2

1

any

0

0

1

0

1

ON

ON

OFF

ON

ON

OFF

ON

3

1

any

0

0

1

1

1

ON

ON

ON

ON

OFF

OFF

ON

4

1

any

0

1

0

0

1

OFF

ON

ON

OFF

OFF

ON

ON

5

1

any

0

1

0

1

1

ON

OFF

ON

ON

OFF

ON

ON

6

1

any

0

1

1

0

1

OFF

OFF

ON

ON

ON

ON

ON

7

1

any

0

1

1

1

1

ON

ON

ON

OFF

OFF

OFF

OFF

8

1

any

1

0

0

0

1

ON

ON

ON

ON

ON

ON

ON

9

1

any

1

0

0

1

1

ON

ON

ON

OFF

OFF

ON

ON

10

1

any

1

0

1

0

1

OFF

OFF

OFF

ON

ON

OFF

ON

11

1

any

1

0

1

1

1

OFF

OFF

ON

ON

OFF

OFF

ON

12

1

any

1

1

0

0

1

OFF

ON

OFF

OFF

OFF

ON

ON

13

1

any

1

1

0

1

1

ON

OFF

OFF

ON

OFF

ON

ON

14

1

any

1

1

1

0

1

OFF

OFF

OFF

ON

ON

ON

ON

15

1

any

1

1

1

1

1

OFF

OFF

OFF

OFF

OFF

OFF

OFF

BI

any

any

any

any

any

any

0

OFF

OFF

OFF

OFF

OFF

OFF

OFF

RBI

1

0

0

0

0

0

0

OFF

OFF

OFF

OFF

OFF

OFF

OFF

LT

0

any

any

any

any

any

1

ON

ON

ON

ON

ON

ON

ON

Notes:

1. BI must be high when output functions 0 through 15 are desired. RBI must be high if blanking of a decimal zero

is not desired.

2. If BI is low, all 7 segments are off, regardless of any other inputs (such as A, B, C, or D).

3. The RBO is typically high. If A, B, C, D, and RBI are all low, and the lamp test (LT) is high, then all 7 segments

are off. In this situation, the RBO goes low.

4. If BI is high, and LT is low, all 7 segments are on. This function can be used to see if all the LED segments are

working.

5. Note that the BI and RBO share pin #4. It is both an input and an output.