4.5 Get Random Action Step

[Craigery]

I would like to have the EndAction/EndAnimation User 0 slot change the object to a Random Action Step. In TimerEndScripts.asm, starting at line 153, I have changed the userEnd0_action to be this:

userEnd0_action:
		LDA Object_frame,x
		ora #%00111000
		STA Object_frame,x
		
		TXA 
		STA tempA
		
		JSR doGetRandomNumber
		STA tempB

		
		DoObjectAction tempA, tempB
		
	RTS

It doesn't appear to work though; am I approaching this wrong or misunderstanding doGetRandomNumber? Thanks in advance.

 

[RadJunk]

You have the perfect idea. The PROBLEM you are having is that right now doGetRandomNumber gives you a number between 0 and 255, and there are only 8 actions. So you need to flag off the high bits.

JSR doGetRandomNumber ;; gets random value between 0 and 255
AND #%00000111 ;; flags off the top 5 bits...now you have what remains between 0 and 7.
                     ;00000xxx will be a value between 0 and 7, because...
                             ;; 000 = 0
                             ;; 001 = 1
                             ;; 010 = 2
                             ;; 011 = 3
                             ;; 100 = 4
                             ;; 101 = 5
                             ;; 110 = 6
                             ;; 111 = 7

STA tempB ;; now tempB is between 0 and 7.  That should give you what you want :-)

 

[dale_coop]

You have the perfect idea. The PROBLEM you are having is that right now doGetRandomNumber gives you a number between 0 and 255, and there are only 8 actions. So you need to flag off the high bits.

JSR doGetRandomNumber ;; gets random value between 0 and 255
AND #%00000111 ;; flags off the top 5 bits...now you have what remains between 0 and 7.
                     ;00000xxx will be a value between 0 and 7, because...
                             ;; 000 = 0
                             ;; 001 = 1
                             ;; 010 = 2
                             ;; 011 = 3
                             ;; 100 = 4
                             ;; 101 = 5
                             ;; 110 = 6
                             ;; 111 = 7

STA tempB ;; now tempB is between 0 and 7.  That should give you what you want :-)

Oh, nice to see you here, Joe <3
(too many members now, on the forum, really difficult to reply to everyone... but glad to see more and more people are confident with code, sharing and helping each others.