assembly code for led

Parth86 · Dec 19, 2013

I have one switch and one LED. the positive edge of switch is connected to port pin PO.1 and negative edge is connected to port pin PO.2 and LED is connected to output the positive edge of motor is connected to port pin P1.1 and negative edge is connected to P1.2

if switch is on then LED is on
if switch is of then LED is of
I am trying to make assembly code please check out code

Code:

org    o h
main:
          jb P0.1,  on
          jb P0.2,  on      ; switch is closed
        jnb P0.1, off       ; switch is open
        jnb P0.2, off
        sjmp main
ON:
        setb P1.1         ;    led on
          clr  P1.2
        sjmp main
OFF:
          clr P1.1           ; led off
          clrP1.2
           sjmp main
end

Ian Rogers · Dec 19, 2013

That's the code I gave you for the motor!!
If you have one LED connected to P1.1
And one switch on P0.1

Code:

org    o h
main:
      jb P0.1,  on      ;   switch is closed
      jnb P0.1, off     ;   switch is open
      sjmp main
OFF:
      setb P1.1         ;    led off
      sjmp main
ON:
      clr P1.1           ; led on
      sjmp main
end

You need to sink the LED on Port 1 ( not sure if they are open collectors.. )

Parth86 · Dec 19, 2013

Ian Rogers said:
That's the code I gave you for the motor!!
If you have one LED connected to P1.1
And one switch on P0.1

Code:

org o h main: jb P0.1, on ; switch is closed jnb P0.1, off ; switch is open sjmp main OFF: setb P1.1 ; led off sjmp main ON: clr P1.1 ; led on sjmp main end

View attachment 82887
You need to sink the LED on Port 1 ( not sure if they are open collectors.. )

let me clear one thing
the positive edge of LED is connected to port pin P1.1 and negative edge is connected to P1.2
so why you are using only one pin P1.1 why you are not using P1.2

Ian Rogers · Dec 19, 2013

Why on earth would you want to use TWO pins to light an LED????

Some pins on the micro can't supply 5v.... All pins can sink current... the pins on a 8051 can only sink / source less than 10mA.... I think only Port 0 can supply as well as sink...

Parth86 · Dec 19, 2013

Ian Rogers said:
Why on earth would you want to use TWO pins to light an LED????

Some pins on the micro can't supply 5v.... All pins can sink current... the pins on a 8051 can only sink / source less than 10mA.... I think only Port 0 can supply as well as sink...

it means i need to connect one pin to controller and other pin to ground

absf · Dec 19, 2013

I can think of one reason why you want to connect both legs of the LED to the 8051. In case someone wants to connect more LEDs to less number of pin on the 8051. In the attached schematic, I can connect 8 LED to 5 I/O pins. With a little more thought, you can connect even more LEDs to the same amount of pins.

Though I've never tried out whether it would work, this was mentioned in one of the Ap notes in microchips " Bag of Tricks". Only problem is that only 4 LEDs can be switched on at the same time....

Allen

Ian Rogers · Dec 20, 2013

absf said:
I can think of one reason why you want to connect both legs of the LED to the 8051. In case someone wants to connect more LEDs to less number of pin on the 8051. In the attached schematic, I can connect 8 LED to 5 I/O pins. With a little more thought, you can connect even more LEDs to the same amount of pins.

Though I've never tried out whether it would work, this was mentioned in one of the Ap notes in microchips " Bag of Tricks". Only problem is that only 4 LEDs can be switched on at the same time....

Allen

Hi Allen!! No I don't think the chip is capable of sinking that much current on a single pin...

absf · Dec 20, 2013

Ian Rogers said:
Hi Allen!! No I don't think the chip is capable of sinking that much current on a single pin...

Yep, you're probably right. So this arrangement is only for "one LED at a time" use.

Cheers to your whisky and Merry Xmas.

Allen

assembly code for led

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