Example of Interfacing Seven Segments LED Display with 8085

Seven segments LED display :

A seven-segment LED is a kind of LED(Light Emitting Diode) consisting of 7 small LEDs it usually comes with the microprocessor’s as we commonly need to interface them with microprocessors like 8085.

Structure of Seven Segments LED :

• The LED in Seven Segment display are arranged as below

• It can be used to represent numbers from 0 to 8 with a decimal point.
• We have eight segments in a Seven Segment LED display consisting of 7 segments which include ‘.’.
• The seven segments are denoted as “a, b, c, d, e, f, g, h” respectively, and ‘.’ is represented by “h”

Interfacing Seven Segment Display with 8085 :

We will see a program to Interfacing Seven Segment Display with 8085 assuming address decoders with an address of AE H.

Note logic needed for activation –

• Common Anode – 0 will make an LED glow.
• Common Cathode – 1 will make an LED glow.

Common Anode Method :

Here we are using a common anode display therefore 0 logic is needed to activate the segment. Suppose to display number 9 at the seven-segment display, therefore the segments F, G, B, A, C, and D have to be activated.

The instructions to execute it is given as,

MVI A,99
OUT AE

• First, we are storing the 99H in the accumulator i.e. 10010000 by using MVI instruction.
• By OUT instruction we are sending the data stored in the accumulator to the port AFH

Common Cathode Method :

Here we are using common cathode 1 logic is needed to activate the signal. Suppose to display number 9 at the seven-segment display, therefore the segments F, G, B, A, C, and D have to be activated.

The instructions to execute it is given as,

MVI A,6F 
OUT AE

• First, we are storing the 6FH  in the accumulator i.e.01101111 by using MVI instruction.
• By OUT instruction we are sending the data stored in the accumulator to the port AFH