setting a bit on a ram variable

[Scorpion Illuminati]

Lets say i have a byte variable called flags. As you know an integer has 8 bits.

7-6-5-4-3-2-1-0

How would I set bit X where x is 0 to 7? For example:

flags       equ (audio_clock+SizeByte)



FLAG_FRET_GREEN       equ 0x1

FLAG_FRET_RED           equ 0x2

FLAG_FRET_YELLOW    equ 0x4



// now set it

??

I want to set a bit without effecting the other ones. Any assistance in this matter would be greatly appreciated.



Sincerely,



Scorpion Illuminati

[Deleted]

Nov 10, 2015 22:35:50 GMT -5 Scorpion Illuminati said:

I want to set a bit without effecting the other ones.

In ASM ( set bit 0 ) ...

bset.b #0,(flags)
In C ( set bit 0 ) ...

flags = flags | 1;
In BASIC ( set bit 0 ) ...

flags = flags OR 1;
BasiEgaXorz doesn't support BYTE variables though. So if you want to use a BYTE ( 8-bit ) instead of a WORD ( 16-bit ) you need to use the READ and WRITE commands.

[Scorpion Illuminati]

Nov 11, 2015 6:32:29 GMT -5 @titan said:

Nov 10, 2015 22:35:50 GMT -5 Scorpion Illuminati said:

I want to set a bit without effecting the other ones.

In ASM ( set bit 0 ) ...

bset.b #0,(flags)

In C ( set bit 0 ) ...

flags = flags | 1;

In BASIC ( set bit 0 ) ...

flags = flags OR 1;

BasiEgaXorz doesn't support BYTE variables though. So if you want to use a BYTE ( 8-bit ) instead of a WORD ( 16-bit ) you need to use the READ and WRITE commands.

Thanks for the info. Am having a bit of trouble figuring out how to use it effectively. Here's the proposed code:



     btst #pad_button_a, d0                                                   ; Check A button

     bne @NoA                                                                       ; Branch if button off

     bset #FLAG_FRET_GREEN, (fret_flags)                             ; set the green fret bit

@NoA:

     bclr #FLAG_FRET_GREEN, (fret_flags)                              ; clear the green fret bit



The problem is no matter what the clear bit instruction executes regardless if the button is on or off. Any assistance in this matter would be greatly appreciated.



Sincerely,



Scorpion Illuminati

[Deleted]

Nov 12, 2015 18:11:52 GMT -5 Scorpion Illuminati said:

The problem is no matter what the clear bit instruction executes regardless if the button is on or off. Any assistance in this matter would be greatly appreciated.

That's because you always flow from BSET into BCLR, you need a BRA that jumps over BCLR after BSET has been executed.

However, what are you trying to do exactly? Why do you have a variable for pad_button_a individually? It seems pretty unnecessary to "split" button bits from the joystick state and then rejoin them again ( if that's what you're trying to do ).

[lunchbox]

Super quick and dirty. Titan is exactly right...

   btst    #pad_button_a,d0                ; test bit
   bne     .NOA							   ; branch if not equal
   bset    #FLAG_FRET_GREEN,(fret_flags)   ; otherwise set bit
   bra.s   .DONE				  		   ; branch to DONE after set

.NOA:
   bclr      #FLAG_FRET_GREEN,(fret_flags) ; clear bit
   ; we fall through from here into .DONE automagically due to program flow...
   ; place a bsr, jsr, jmp command here to go somewhere else after clearing bit..
.DONE:
  rts  ; return maybe?

[Deleted]

#FLAT_FRET_GREEN? Are you making Guitar Hero MD?

[Scorpion Illuminati]

Nov 16, 2015 16:25:57 GMT -5 @elusive said:

#FLAT_FRET_GREEN? Are you making Guitar Hero MD?

No I'm making a rhythm game.

Sincerely,

Scorpion Illuminati

[Deleted]

Lol what's the difference?