Thread: bitwise? am i right?

i wish to check whether the bit i in the data word "Address" is "1" or "0". So i decided to use for loop and bitwise. But I'm not sure if the code is correct. My address is 0b0110000111010110. Heres the code:

Code:

unsigned char a = 0b000000000001;
for (i=0 ; i < 16 ; i++)
{	
      //checks whether the bit i in the data word "Address" is "1" or "0"
      if (Address && a) !=0   // ==> True if Bit 1 is a logic "1", else False
     {
          // output a logic "1":
          for (j=0 ; j < 21 ; j++)
         {
	G1_LED2	= 1;
      	DelayUs(9);
      	G1_LED2	= 0;
      	DelayUs(9);
         }
            
                 DelayUs(1690);
     }
     else
    {
         // output a logic "0"
         for (j=0 ; j < 21 ; j++)
         {
	G1_LED2	= 1;
      	DelayUs(9);
      	G1_LED2	= 0;
      	DelayUs(9);
         }
               
         DelayUs(560);
    }	
    a = a <<1;
    i++;
}

Is the above code correct?
Im currently using MPlab and seriously, i do not know what compiler i am using. Any recommendations for compilers that i can download frm the net?
Thanks!!

You're not using i in any form or fashion, so you're not checking bit i. Currently you're checking bit 31 (the LSB) a bunch of times. You need to change a/use i somehow to get different bits.

but I thought I already use i++ and that a is updated at each time of the loop? So I thought, during the first loop when i =0, the address is being compared with 0b000000000001...and after a = a<<1, a becomes 0b000000000010. and after i++ , it goes to the second loop and the addresss will now be compared with 0b000000000010...and so on..

sorry but correct me if I'm wrong here. And if you could give me an example, it would be best. Thanks once again.

Originally Posted by skiz

but I thought I already use i++ and that a is updated at each time of the loop? So I thought, during the first loop when i =0, the address is being compared with 0b000000000001...and after a = a<<1, a becomes 0b000000000010. and after i++ , it goes to the second loop and the addresss will now be compared with 0b000000000010...and so on..

sorry but correct me if I'm wrong here. And if you could give me an example, it would be best. Thanks once again.

No, you're right. I started to glaze over when the else looked the same as the if and didn't see it down there. So yes, a starts at the least significant bit and moves over. However you are adding to i twice (once in the control of the for-loop and once at the bottom of the loop itself).

However you are adding to i twice (once in the control of the for-loop and once at the bottom of the loop itself).

Code:

for (i=0 ; i < 16 ; i++)   <<<< u mean here?
{     ......
       ....
       i++;                       <<<< and here?
}

what shd i do? hmmm..

oh..or do i just delete off i++? hehe...sorry i'm bad at this.

Well a silly question here as i got u only need to check the bits in ur address. then why do u need a at all.. and whats the purpose of this if (Address && a) !=0 ????

actually, i just realize my own silly mistake.
it shd be:

Code:

if ((Address && a) !=0)
{
.....and so on...
}

and well, if I do not include a, how do I check the address bits? coz my program is such that if the result is 0, means the bit checked is '1' (since I AND it)..and my program needs to function such that if bit '1' is detected, it will delay for 1690us ..and if bit '0' is detected, it will delay for 560us.

O_o I don't know if I'm making any sense to you in what I have just said. haha..

Yes Boss got it

OK great! thank you tabstop and stevesmithx!!
...and also rits for ur concern. haha..

but now when I build the program, it gives this error:
Error [1347] ; 0. can't find 0x90 words (0x90 withtotal) for psect "text76" in segment "CODE" (largest unused contiguous range 0x31)

Don't even have an idea what's that all abt. But anyway, i guess questions related to this problem should not be pose here! so thanx ppl! !