PathPartner Technology Xillinx Software Engineer for VLSI interview questions

I m from m.tech vlsi background. They cald me fr interview. I thought of it as completely software and i prepared c language well. But they put test on vlsi, basics of switching theory and logic design. Test with 25 ques with multivibrator, flipflops, gates, etc. I got qualified and cald fr interview after 15 mins. They askd abt the ques dat was in test. Den dey askd me to write xillinx code. Little bit i wrote. Askd sychronous nd asynchronous difrence. I dint say. Dey reject