/* C function which passes a parameter to my routine */
void routine_a(unsigned char c)
{
   _asm
   ; how can I access my variable c from here to put it into the acc 

   ljmp MY_ASSEMBLYROUTINE
   _endasm;
}

/* reverse one - getting a result back */
void routine_b()
{
   _asm
   ljmp MY_ASSEMBLYROUTINE_WITH_RESULT
   ; how can I achieve the same as return(...); with the contents of Acc after my routine?
  _endasm;
}