my ep3s200f1152 has been damaged?

[Altera_Forum]

Hi,on my subboard there is a fpga(ep3s200f1152),now i cannot access jtag chain,as download is also not work,yesterday i had used it and it can work .My subboard is connected to bottom board which provides the power to fpga,when i plug other subboard on the bottom board fpga can download and work correctly. Now i suspect that the fpga is damaged, 

1 when i test the resistor value between tck and gnd, I found that : wrong fpga is about 170ohm and correct fpga is about 1.8Mohm, 2 wrong fpga consume more current than correct fpga with vcc25 power supply,about 50ma is my suspect correct?By the way,I have hot plug the jtag cable,is it contribute the fpga damage?

[Altera_Forum]

170 ohms to GND from the TCK is far too low. So, I suspect you have damage to the FPGA. 

 50mA doesn't necessarily sound that bad but if it's much more than a known good unit, it doesn't look good for your 'wrong' FPGA.  Yes - you can hot-plug suitable JTAG cables. That won't cause a problem.  Regards, Alex

[Altera_Forum]

Just my experience with hot-plug of anything. If you can ensure the GND lines to be connected first - either by special connectors or by using a wire clamp you can hot-plug these stuff. Otherwise the signal voltages on the JTAG Signal lines can increase due to Floating GND potentials (which are most often "somehow" connected either capacitive, by earth groud references, ...) 

The datasheet (iirc the cylcone IV one) has some protection diodes connected to the signals to keep the voltages in acceptable range. If you really need to hot-plug the JTAG cable I'd recommed to either route GND by a separate line to equalize signal references or to add the protection diodes.