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cassemblybit-manipulationwinavrmotordriver

Set a one bit in an 8-bit PIN without changing the other bits

Using winAVR for the following code.

I got an 8-bit PIN here that I need to OR it with 00000010 or 0x02 to set the 7th bit.

Now what I have to do is the following :

  • Set Port B bit 7
  • Wait for 1ms
  • Clear port B bit 7
  • wait 19ms

BUT, I shouldn't change the other bits in these steps.

So I have to :

  • Read port B
  • Set bit needed
  • write the modified value back to the port
  • Clear bits
  • Write back to Port B

So my test code is :

B=PINB|0x02
Loop delay for 1ms
BP=PINB&0x00
Loop for 19ms

But I think that the other bits are going to be altered in this process, my question is, HOW am I supposed to manipulate one bit of an 8 bit port without changing the other bits ?

Thanks alot !!

Solution

  • You need BP=PINB & ~0x02 The ~ operator is logical NOT. The and operator keeps only the bits other than 2.