Rather than building an EJTAG interface, I recommend the Raven EJTAG interface. It plugs into your LPT port, and will plug into the EJTAG interface on your DBAu1500 board.
I can recommend the Abatron BDI-2000 (www.abatron.ch). It's a powerful, flexible tool that will work in a variety of development environments. In addition to providing debugging features, it also has built-in flash programming algorithms. You can erase/program flash with simple console or script commands from various file formats transferred over the network using tftp.
-- Dan
