Hallo Sundar,

only telling that

the controller is sending garbage characters

is not enough to make a detailed analysis.
Is microcontroller sending the wrong characters, but frames (stop bit a.s.o.) and timing is ok? Are there sharp edges? Are logic levels ok? Does microcontroller hang-up?
I would proceed with sending only one databyte, running in a loop. Again, and again, allways the same databyte. Then with the help of oscilloscope you can see WHAT is wrong.
By the way, 17.4MHz is a rahter high frequency. Is your PCB proper designed?
Are there perhaps some timing errors when contacting external circuitry (RAM e.g.)? Is your oscillator well running? Is frequency ok? Did you perhaps have choosen wrong quartz (overtone type instead of fundamental)? Did you use correct capacitors arround quartz?

We need more details.

Bye,
Kai