Standard entry code for procedures and functions is as follows on the 680x0 architecture:
move.l a6,-(sp) move.l sp,a6
The generated exit sequence for procedure and functions looks as follows (in the default processor mode):
unlk a6 rtd #xx
Where xx is the total size of the pushed parameters.
To have more information on function return values take a look at section 6.1, page 391.