Define.. want to understand

[Ayne]

Can we define a constant to our SFR like below???

&

supose i define a constant x = PORTB,3 like below

#define   x     PORTB,3

if i change the the value of x then the whole PORTB will effected or just bit 3 of PORTB will be effected??

movlw   b'10110110'
movwf   x

what will be the result ???

PORTB = 10110110

OR

PORTB.3 = 0

 

[eblc1388]

In your case, occurance of "x" will be replaced by "PORTB,3" before the source file is processed by assembler or compiler.

If you change the #define to other things, "x" will be substituted by other thing too.

You code does not make sense.

movlw   b'10110110'
movwf   x                ;<<<< wrong !!!

because it substituted into "movwf PORTB,3" and movwf moves 8-bit at a time.

Your remaining questions have nothing to do with the above ASCII replacement.

 

[Kitt354]

If you want to change PORTB,3 use
bsf PORTB,3 or
bcf PORTB,3

 

[Nigel Goodwin]

Essentially all define and equate do is a simple text substitution during assembly, as do those in the inc file. In your example, because it makes no sense, the assembler will generate an error.