Post by thread:Using a variable to clear a bit => Shadow

Mik Kim wrote: > Also, don't use bit operations on PORT. Instead of bcf, you might do > movf PORTB, W > movwf tempB > bcf tempB, 0 ;must use literal as bit position > movf tempB, W > movwf PORTB You've got the wrong idea on this one, I'm afraid. Your "solution" is no better than the simple "bcf PORTB,0". The danger here is that the port may read as something other than what you write to the output register, for various reasons. So, you *don't* read it at all (unless you want to read an input). Your "tempB" above is called a "shadow register", initialized to begin with and again with what you want PORTB to be at any given time. I.e.: start movlw initial_value ; constant movwf tempB ; into shadow movwf PORTB ; and "real" ; somewhere amidst the code ... bcf tempB, 0 ; adjust the shadow; bit 0 cleared here movf tempB, W ; and transfer movwf PORTB ; to "real" -- Cheers, Paul B.