You'll need some kind of ROM to store a minimal boot-loader that will enable you to load your "test code" into RAM. When you say an "rs232 module", does it emulate a 6551 type serial interface, or something else?
Check in the source code repository, under I/O techniques for Ross Archer's Intel HEX downloader. There is also an XMODEM file transfer program there that I wrote. These would be a good place to start.
On a side note, I'd be interested in seeing the code for your FPGA, as I'd like to design a small SBC using FPGA technology.
Daryl
http://65c02.tripod.com/