checkpoint monitor

I am trying to make a monitor that acts like a checkpoint, but when I do so, all it does it take my rings, any help here, this is my code, I am very new to this so yes I aint exactly smart with asm.



Obj2E_ChkS:
cmpi.b #7,d0 ; does monitor contain 'S'


jmp Cont_GotoLevel ; start from monitor


jmp (playsound).l



thanks for your help in advance.

 

"Good evening ladies and gentlemen to another night of the "Jester Show", tonight my guests are beq, bne, blt, ble, bgt and bge."


I would suggest you search google for an MC68000 programmers manual, it's very helpful to have one around if you get stuck in a situation like this one. Try some of the below...


beq (branch if equal)


If 07 is in d0, it will branch, if it is not 07, it will not branch and will continue as normal.




cmp.b #$07,d0 ; is 07 in d0?


beq.s Cont_GotoLevel ; if so, branch to "Cont_GotoLevel"


; otherwise, continue down



bne (branch if not equal)


If 07 is NOT in d0, it will branch, if it is infact 07, it will not branch.




cmp.b #$07,d0 ; is 07 in d0?


bne.s Cont_GotoLevel ; if not, branch to "Cont_GotoLevel"


; otherwise, continue down



blt (branch if lower than)


If d0 is lower than 07 (if it's 06 or 05, etc), it will branch, if it is 07 or higher, it will not branch.




cmp.b #$07,d0 ; is there a value lower than 07 in d0?


blt.s Cont_GotoLevel ; if so, branch to "Cont_GotoLevel"


; otherwise, continue down



ble (branch if lower or equal to)


If d0 is 07 or lower, it will branch, if it is higher that 07 (i.e. 08, 09, etc), it will not branch.




cmp.b #$07,d0 ; is there a value 07 or lower in d0?


ble.s Cont_GotoLevel ; if so, branch to "Cont_GotoLevel"


; otherwise, continue down



bgt (branch if greater than)


If d0 is higher than 07 (i.e. 08, 09, etc), it will branch, if it is 07 or lower, it will not branch.




cmp.b #$07,d0 ; is there a value higher than 07 in d0?


bgt.s Cont_GotoLevel ; if so, branch to "Cont_GotoLevel"


; otherwise, continue down



bge (branch if greater or equal to)


If d0 is 07 or higher, then it will branch, if it is lower than 07 (06, 05, 04, etc), it will not branch.




cmp.b #$07,d0 ; is there a value 07 or higher in d0?


bge.s Cont_GotoLevel ; if so, branch to "Cont_GotoLevel"


; otherwise, continue down



"...and that's all we got time for folks, next week we'll be meeting bpl, bmi, bcc and bcs, goodnight everyone!"

 

I've bumped into instances like this though:



cmpi.w 1F,$1C (d0) ; is blah blah blah
beq.s HellNaw ; if not, branch



So, just be careful. :\

 

I hope the Jester Show becomes a regular segment. Seriously. Just throwing it out there, though...


That being said, the Helpful Links sticky actually has a 68k programmer's manual, as well as the actual Motorola 68k documentation. You should really read these so you don't have to ask these questions.


Also, I doubt that the second part of your code is useful. I don't know the surrounding code, but I am not so sure it matters.



Obj2E_ChkS:
cmpi.b #7,d0 ; does monitor contain 'S'


jmp Cont_GotoLevel ; start from monitor


jmp (playsound).l



Where you have the jump to playsound, it won't do anything because (assuming you fix your Cont_GotoLevel branch), you have not specified a sound in d0 and sound #7 will be played, meaning nothing will be played. You'll want to specify a sound in d0 (by moving a sound number to d0) if you want one played.


Dandaman, the reason for the opposite branch that you're talking about is usually used for the tst function, most often with RAM flags. It is also used for when something is tested for being equal to 0 and has to do with flags usually. Here's an example:



tst.b ($FFFFFFFB).w ; Is the character move flag on?
beq.s DoStuff ; if not, branch



Obviously I'm just using that RAM address as an example, but the tst function checks to see if something is equal to the value 0. I've seen instances of it being used on values not equal to 0, the branch works because the flag is not on and is equal to 0. It is really awkward to explain, but I hope I made some sense.