MAX V "Jtag chain problem detected"

Thanks for the update. Glad to hear you got it working.

Mine is working reliably now as well. I added a 1nF capacitor between TCK and GND to slow down the edges. Even though it works, the signal looks like crap compared to what it was before. The clock now looks like a shark tooth rather than a perfect square wave. 1nF is probably too much and I'll probably try 10pF or 100pF.

With that said, I suspect it is the StratixIV causing my problems. Even when extra devices are shown the MaxV (last device in chain) almost always appears correct. The JTAG seems extremely sensitive to the TCK signal. As I said before, the signal integrity was almost perfect when looked at with the scope (only 3.9pF load). Further, I have a few identical modules and I don't see this issue on all of them. I'd be curious to know if anyone else has seen similar issues. The datasheet lists 180mV hysteresis for the TCK pin and I honestly can't see the ripple coming anywhere close to that at any point from what I see on the scope, however, it also works with the scope attached.