5 7-segment display with 8051

Discussion in 'Embedded Systems and Microcontrollers' started by elyson, Aug 7, 2008.

  1. elyson

    Thread Starter New Member

    Aug 7, 2008
    7
    0
    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?
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,348
  3. elyson

    Thread Starter New Member

    Aug 7, 2008
    7
    0
    I see, but i do need more reference for my exercise still, any good site to recommend?
     
  4. nanovate

    Distinguished Member

    May 7, 2007
    665
    1
    What more do you need?
     
  5. binu_ji

    Member

    Jul 13, 2007
    22
    1
    Multiplexing saves pins, else you should use 5 nos of 7447. So you need 20pins.
    Normal 8051 micros have 32 i/o lines.
     
  6. elyson

    Thread Starter New Member

    Aug 7, 2008
    7
    0
    Isnt port 3 reserved for special purposes? So that means 8051 only got 3 times 8 =24 I/O pins.
     
  7. RiJoRI

    Well-Known Member

    Aug 15, 2007
    536
    26
    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
     
  8. amolhshah

    Member

    Aug 12, 2008
    13
    1
  9. Arm_n_Legs

    Active Member

    Mar 7, 2007
    183
    10
    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).
     
  10. brijbhoomi

    New Member

    Aug 27, 2008
    2
    0
Loading...