Thank you for your reply again Akira,
Yes , i did an experiment based on a book which teaching me how to build an SOPC.
This book is using EP1C20F400C7 of Cyclone Family, and I am using EP3C16F484C6 of Cyclone III family (DE0).
The project which is given by the CD of the book ALREADY HAVE their pin assignments, including the unused pins(for EP1C20F400C7 of Cyclone Family of course). Since i have to change the device, all of the pin assignment will be deleted. So i am a bit confused if RS232 should be assigned as output or input and where to be assigned?
Yes, DE0 board doesnt have any RS-232C but it has RS-232 port, right?
Thank you,
Yuyex:o