Selbi's little questions

EDIT: It seems like I have a question every day. So instead of bumping this forum with thousands of question threads I'm using this one now.


I have this:



SomeRoutine:
move.w ($FFFFFFF1).w,d0 ; move adress 1 to d0


move.w ($FFFFFFF2).w,d1 ; move adress 2 to d1


cmp.w d0,d1.w ; compare d0 and d1


beq.s SomeRoutine_IfEqual ; branch if equal



My question is, can I reduce the first 3 lines to 1? I've tried this:



SomeRoutine:
cmp.w ($FFFFFFF1).w,($FFFFFFF2).w ; compare the 2 adresses


beq.s SomeRoutine_IfEqual ; branch if equal



But then I get the error Illegal adressing mode (for the cmp). I looked through my ASM and found the same for move:



move.w ($FFFFFFF3).w,($FFFFFFF4).w ; move adress 1 to 2



And this works. So, how can I so the same for the cmp? If you know, how to reduce it to 2 lines, don't tell me, because I just want 1 singel line.


Hopefully someone knows how to do this.

 

move.w ($FFFFFFF1).w,d0 ; move adress 1 to d0


move.w ($FFFFFFF2).w,d1 ; move adress 2 to d1


cmp.w d0,d1.w ; compare d0 and d1


beq.s SomeRoutine_IfEqual ; branch if equal



Alrighty, first of all, you're trying to move FFF1 and FFF2 when you move the address to d0, you're specifying word length, not byte (move.w, you probably want move.b), which won't work. Accessing odd RAM addresses as words doesn't work (maybe on some emulators, not real hardware). Secondly, you would be able to do it with:



move.b ($FFFFFFF1).w,d0
cmp.b ($FFFFFFF2).w,d0


beq.s SomeRoutine_IfEqual



I don't believe there's anything less than that that would work.

 

There's nothing shorter? That sucks. However, thanks to the information. But what about .b and .w? Where is the problem when I use .w (I have problems with all these .x things... even with .s for branch commands)?

 

For not branching commands, .b and .w tells the size. For example, $FFFFFFF1 should be just .b, because if you use .w it will us $FFFFFFF1 and $FFFFFFF2 because those two bytes are equal to a word. If you used .l you'd be using $FFFFFFF1 all the way to $FFFFFFF5 (each thing of ram is worth one byte, a long word is worth four bytes). Real hardware isn't able to take an odd address (F1 is abbreviating the RAM) such as F1 and use it as a word. Words and long words have to be an even number.

 

Aha ok. But what is this .s doing? I know, when I have it in a branch, I can't jump very far away, usually only up to 5 labels. Does it mean "Short" or something like this?

 

Yes, it means short.


.l means long and .w means word I think.

 

Another question:


Is it better when I use:



clr.b ($FFFFFFFF).w ; clear something



Or:



move.b #0,($FFFFFFFF).w ; move o to something



Technically seen the same thing is happening, but what's better to use?

 

I personally suggest clr.b, myself; if I remember correctly, it saves you a byte or two in-ROM compared to moving #0 to any given address.


If you're working with registers, I suggest using moveq instead--it's not only smaller, but it's quite a bit faster as well.

 

Ah Ok. About moveq, I personally don't like this command... exspecially because I can't have more than $8... but Ok.


Another question: How can I check if Sonic is on the ground and is not moving?

 

After checking $22(a0) to make sure that Sonic is standing on the ground (in other words, not in the air), do a check against his inertia value to make sure that it's $0; if it's not, then don't execute the move.


Something like this should do:



CheckShit:
btst #1,$22(a0) ; check if Sonic is in the air


bne.s GetOutFaggot ; if he is, get the fuck out


tst.l $10(a0) ; check X and Y speed


bne.s GetOutFaggot ; if Sonic is moving, then get out


tst.w $14(a0) ; check inertia


bne.s GetOutFaggot ; if Sonic has potential to move, then get out


DoShit:


put whatever here


GetOutFaggot:


rts



You may be able to get away without checking inertia; I'm not entirely positive. I'm also not sure if you use tst with a long; if you can't, then change it to cmp.l or something.

 

This was the greatest example in the world, and for 90% it works! Thanks Tweaker. Hope you can help me for my next problem, which is currently not there....

 

Ok, another question: How can I check if Sonic has running animation? This is my example:



XCode:
*unknown code* ; does sonic has the running animation?


bne.s CheckStuff ; if not, branch


move.b #1,($FFFFFFFF).w ; set CheckStuff flag


CheckStuff:


tst.b ($FFFFFFFF).w ; was XCode flag set?


beq.s Exit ; if not, branch


move.b #2,($FFFFFFFF).w ; if yes, do this


Exit:


rts



I guess it's a bad example, but that's no problem, since I just want to know the check for running animation. I don't want a velocity check, because in my code somewhere above this check, my velocity got replaced.

 

cmpi.b #$1,$1C(a0) is the running animation (since 1 is the running animation) but you could always check for the speed of sonic ($600 while he is running).

 

cmpi.b #1,$1C(a0) doesn't work correctly. He's always branching, because this isn't the correct code. So I will try it with checking Sonic's speed.

 

Ok, another question: Where is the code for setting the position for the Live Counter? Or better, where is the code for the live counter?

 

Ok, I found the code for the numbers. But, where is the code for the Sonic Icon? I searched for it and found Nem_Lives, but there's nothing, which jumps to this line... where is the code for loading the Sonic Live Icon?

 

It loads from ArtLoadCues (Pattern load cues.asm)

 

Time to bump my topic.


However, this is a really small question, but I want to know it: What are the branch commands bpl, bhi and bmi doing? I'm sure they are listed somewhere on Retro, but I can't find them. So I ask along here.


Qjimbo edit: Before anyone else makes the same mistake, this has been answered on page 2...

 

Yes, that page is quite buried down, I needed like 15 minutes to find it myself, perhaps more wikilinks would help, but hey, not by problem. Here it is, by the way: http://info.sonicretro.org/SCHG:68000_Instruction_Set. Scroll down

 

http://sonicresearch.org/68k/Bcc.html


This any help?


EDIT: That'll teach me to leave topic windows open for several minutes...