trouble with S12XS SCI controller

i'm developing an uart driver based on interrupts.
i've realized that when executing the ISr software failed to reset TDRE Flag.i made sure tha i've followed all steps listed in the datasheet to do so which are:

1-reading the SCI Status Register.
2-Writing to the SCI Data Low register.

but the ISR Continue to go in Loop.

i wish tha anyone could help me figure this out.