I can't find an FPGA on the DIO2, but the programming circuit is probably sound. I'd be careful, however, and ensure that the programming circuit meets the spec's set forth by XILINX themselves.

There's an app-note somewhere ... Hmmm ... here it is ...

I've had no trouble with the JTAG interfaces that Digilent has built into their boards. I've had no trouble with the ones that others have built for use with JTAG. On a lark, I bought one from a Canadian company, that cost ~$26CN including shipping, IIRC, and works just fine, too, though its "flying leads" are a mite flimsy.

If you carefully reproduce the circuit on the Digilent board, having understood the basics of how JTAG connections must be implemented, I think you'll have no trouble reproducing their work.

I'd recommend you take a careful look at some of the later DIGILENT boards, particularly ones that use the circuit that you intend to program. I personally have a number of Digilent boards and the programming cables that came with them, and they all seem to work just fine. All they have done in the later boards is conform to a widely used standard pinout, promoted by XILINX. If you look at

http://www.xilinx.com/support/s...d/jtag.pdf

I think you can figure out how to build an equivalent cable with minimal risk of vailure, and of damaging anything.

As you've probably seen many times, DON'T DEVIATE FROM THE RECOMMENDED SCHEMATIC! If you fail to heed this advice, you're on your own.

BTW, there's a slight drafting error on the schematic, namely that both U1 and U2 are 'HC125's, which should tell you that you probably CAN use both halves of a 74HC244 independently as the DIGILENT people have done ... and the term serial, just to avoid confusion, refers to serial numbers.

Now, the Digilent folks did things a bit differently, but if you study both circuits, you'll see what's necessary. I'd point out that the function is what matters, and that the DIGILENT hardware works fine with the XILINX programming software (IMPACT).

RE