trouble with MC9S12XS SCI controller

[darlint]

i'm developping an uart driver based on S12XS SCI controller .driver manages interrupts and call back events.

I've realized that when executing the ISR routine soft is unable to reset TDRE Flag so the ISR continue

going in loop.I've really followed Steps listed in datasheet which are:

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


i wish tha anyone could help figure this out.