Frist, thankyou your advises,Sebastian and Tomi Engdahl. It's useful.
I've design a DMX512 transmiter(using atmega128). It worked. Now, i want it have a rom memory to store DMX512 values so the transmiter can stand alone. So, what kind of memory i need?

And i have just bought a dmx512 kit from Sunlight(France). It's great, both of software and hardware. But it's too expensive. I think that it be a good product. In my country(Viet Nam), u can sell a lot if it's cheeper. So i want design a product what based on it.
Do u have any advise(about hardware and software)?
Thanks very much!!!