The HC08 uses the C calling convention for all functions. The caller pushes the arguments from left to right. After the call, the caller removes the parameters from the stack.
When a function contains a fixed number of arguments and the size of the last parameter is two bytes, the HC08 passes last parameter in X and A.
When a function contains a fixed number of arguments and the size of the last parameter is one byte and the size of the next to last parameter is greater than one, the HC08 passes the last parameter in A. When the size of the next to last parameter is also one byte, the HC08 passes the next to last parameter in A and the last one in X.