7 Segment Display interface on I/O ports

March 22, 2011 — Leave a comment

For the seven segment display you can use the LT-541 or LSD5061-11 chip. Each of the segments of the display is connected to a pin on the 8051 (the schematic shows how to do this). In order to light up a segment on the the pin must be set to 0V. To turn a segment off the corresponding pin must be set to 5V. This is simply done by setting the pins on the 8051 to ‘1’ or ‘0’.

7-SEG  Display are available in two types -1. Common anode   &   2. common cathode ,  but command anode display are most suitable for interfacing with 8051 since 8051 port pins can sink current better than sourcing it.

 

For displaying Digit say 7 we need to light segments -a ,b, c. Since we are using Common anode display , to do so we have to to provide  Logic -0 (0 v) at anode of  these segments.

so need to clear  pins- P1.0 ,P1.1,P1.2.    that is 1 1 1 1 1 0 0 0 –>F8h .

CREATING DIGIT PATTERN

For displaying Digit say 7 we need to light segments -a ,b, c. Since we are using Common anode display , to do so we have to to provide  Logic -0 (0 v) at anode of  these segments.

so need to clear  pins- P1.0 ,P1.1,P1.2.    that is 1 1 1 1 1 0 0 0 –>F8h .

Connection

Segment number 8051 pin number
a P1.0
b P1.1
c P1.2
d P1.3
e P1.4
f P1.5
g p1.6
h(dp) P1.7

You can also do this for some characters like A ,E .. but not for D or B because it will be same as that of  0 & 8 . So  this is one of limitation of 7-seg display.

Since we can Enable only one 7-seg display at a time ,we need to scan these display at fast rate .The scanning frequency should be high enough to be flicker-free. At least 30HZ .Therefore  – time one digit is ON is 1/30 seconds

INTERFACING

Note that I am using Common Anode display. so the common Anode pin is tied to 5v .The cathode pins are connected to port 1 through 330 Ohm resistance (current limiting).

Common Anode display



Source: maheshwankhede

Jagan

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