microcontroller for programming FPGA over JTAG

Although the USB-Blaster protocol is undocumented, there is this project:

http://ixo-jtag.sourceforge.net/archive/ixo_de_usb_jtag.html

This link is the same project that FvM pointed you to in the other thread.

Also take a look at the debugger core on OpenCores.org:

http://opencores.org/project,adv_debug_sys

It looks like someone has figured out how to control the USB-Blaster as a general purpose debugger. You could use this to figure out the software interface to a real USB-Blaster, and then emulate with your micro.

I've not looked at this stuff, so I have no idea whether it works. I am interested in hearing if you have any success ...

Cheers,

Dave