Reverse REFP0

[Primordial Ooze]

I'm trying to reverse the sprite when it intersects the left or right boundry. Here is the code i am using:

sec

lda #$08

sbc REFP0

sta REFP0

However it only seems to work once. Any assistance would be greatly appreciated.

 

Sincerely,

 

Primordial Ooze

[+SpiceWare]

REFP0 is a write only register. I believe when you read from it you're really reading a mirror of INPT4.

 

It's better to use EOR to toggle bits.

 lda MEMORY
eor #$08
sta MEMORY

 

To do what you want, try something like this:

 MY_REFP0 = $80 ; use a RAM location to save the state
lda MY_REFP0
eor #$08
sta MY_REFP0
sta REFP0

Edited October 29, 2012 by SpiceWare