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reading and skipping from port

rocknmoon rock

Hi All,,

I am trying to write a simple program that do the following.

it increments a 3-bit binary number after a delay. It looks like following.

do{

if (bin_num++ > 0x7) bin_num=0;
deley();

}while(1)

Now what i want to do is that , read Port 1, and if any bit is Zero (for example if P1^3 is zero) then leave skip the number 3 in incrementing bin_num. So the bin_num will count as 0, 1, 2, 4, ..

Any quick idea how to best do this ??

Any help would be great.

Thankzz && Bye
-Rocknmoon

Parents
  • 0

    What a curious problem. I have not tried this, but it should get you on your way.

    It is easy to check for any 1s in a word by adding to that word a word full of 1s and looking for overflow e.g. 

    skip = ( P1 + (unsigned int) 0x00FF ) > 0x00FF;
    Its one of those things that is even easier in assembler...

    You want to check for any zeros in P1 so just complement P1 in the test.
    skip = ( ~P1 + (unsigned int) 0x00FF ) > 0x00FF;
    So you will end up with something like:
    do
{
    skip = ( ~P1 + (unsigned int) 0x00FF ) > 0x00FF;
    bin_numm++;
    if ( bin_num == 0x08 ) bin_num = 0;
    if ( ( bin_num == 0x03 ) && skip ) bin_num++;
    delay();

}while(1)
    Have fun.

Reply
  • 0

    What a curious problem. I have not tried this, but it should get you on your way.

    It is easy to check for any 1s in a word by adding to that word a word full of 1s and looking for overflow e.g. 

    skip = ( P1 + (unsigned int) 0x00FF ) > 0x00FF;
    Its one of those things that is even easier in assembler...

    You want to check for any zeros in P1 so just complement P1 in the test.
    skip = ( ~P1 + (unsigned int) 0x00FF ) > 0x00FF;
    So you will end up with something like:
    do
{
    skip = ( ~P1 + (unsigned int) 0x00FF ) > 0x00FF;
    bin_numm++;
    if ( bin_num == 0x08 ) bin_num = 0;
    if ( ( bin_num == 0x03 ) && skip ) bin_num++;
    delay();

}while(1)
    Have fun.

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