As the title say, i need to design a circuit with 5 7-segment display using 8051 as exercise. As i had known, 8051 only got 16 output in total in port 0 and port 2, and since each 7-segment display need 7 output, it is obvious 8051 output isnt enough. I recently found out a chip called IC 7447 that will that take in BCD input and convert it to 7 output required by the 7-segment display. But this is still limited, as you see, BCD for 7 output require 4 output and 5 7-segment display needs 20 output and 8051 only got 16. Simply put, any solution to this, when output of 8051 isnt enough?

 

Hello,

You could use multiplex to drive the 7 segment displays.
Here is an example how to do it.
http://www.kmitl.ac.th/~kswichit/clock/clock.htm

Greetings,
Bertus

 

I see, but i do need more reference for my exercise still, any good site to recommend?

 

I see, but i do need more reference for my exercise still, any good site to recommend?

What more do you need?

 

Multiplexing saves pins, else you should use 5 nos of 7447. So you need 20pins.
Normal 8051 micros have 32 i/o lines.

 

Isnt port 3 reserved for special purposes? So that means 8051 only got 3 times 8 =24 I/O pins.

 

For the 74xx47s, you need 4 pins for the data bus, and either 5 pins for display selection, or 3 pins if you use a 74xxx138.

At the worst -- driving the displays directly from the micro with no support chips -- you would need 12 pins: 7 for the data, and 5 for display selection.

The 8051 uses ports 0 and 2 for external memory access if you are not using the on-chip memory, or if the internal memory is not large enough. Port 1 (and sometimes 3) have alternate functions such as serial I/O pins. If you're not doing serial I/O, then the pins can be used as normal I/O pins.

--Rich

 

port 3 is not reserved for special purpose it can also be used as general input output.
no need of using IC's or different data lines for each segment just use multiplexing technique saves a lot of data lines
check this link for multiplexing technique
http://www.dnatechindia.com/index.php/Tutorials/8051-Tutorial/7-Seg-Interfacing.html

 

Alternatively, you can use special IC like SAA1064 (4-digit LED-driver with I2C-bus interface). Drive it with the IIC port on some 8051s (such as Atmel AT89C5131).

 

lookout fro www.mytutorialcafe.com