Reading the reference manual for MC9S12XEP100 (probably same goes for many other devices), I noticed that there are two very similar methods to generate interrupts on fixed intervals: The Real Time Interrupt (RTI) on the Clocks and Reset Generator module, and the two Periodic Interrupt Timer (PIT) modules.
It seems that the PIT can do everything that the RTI does, and more. Is there some reason why one would like to use RTI instead of PIT? Maybe to consume less power? Or is RTI included only to maintain backwards compatibility? I have seen both interrupt sources used in software to do very similar things.