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well the VCCA is why the slogan "you need just two voltages for the FPGA" some time ago is not valid when you have to interface with 3.3V logic... I struggled once on this "you need to connect VCCA to 2.5V" also on my first Cyclone II board...
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Yeah, there are a lot of traps in FPGA design, like pll config etc. I wish I could say this mistake is because it is my first board, but it is because it has been awhile since I did an FPGA board.
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While I have currently no clue for the nStatus (assuming there is only the FPGA and the Pull-Up on the line)
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Checked again, nStatus is only connected to 10k pullup to 2v5.
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the "wrong" identification on JTAG is ok... Strange enough the ID reported by the Cyclone IV and III are identical thus the "Auto detect" reports a Cyclone IV as a Cyclone III - you have to correct this to proceed with JTAG configuration...
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Ok, that is sort of good news. So the detection as an EP3S16 is normal for autodetect. I will remember to fix in programmer. This could have bugged me for a while, thanks for mentioning it.
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Referring to ohmic measurements on FPGA pins - be careful when you are using a standard DMM - ohmic measurements are taken (normally) by application of voltage and measurement of currents.. If the DMM applies a measurement voltage above 3.3V, this will either result in internal clamping diodes on the FPGA (which are normally not active w/o being configured) or other I/O structure to get conductive... Sometimes with predamaging the I/O structure - just as a hint...
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Yip, noted, I suppose I could have damaged the pin, BUT I only measured this after it did not work. Also, I think it is highly unlikely that such a sort event would harm the device. But will keep it in mind.
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Nevertheless there is something tying TDI to GND (most likely the Blaster - are there not even some pulses? E.g. on "Auto-Detect"?)
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I put the scope on again, Ch2 on TCK and CH2 on TDI. both normally low (TDI should be high) and this is the case with BB plugged or unplugged. Plugging BB in and running detect has clock signal toggling but nothing on TDI. Well, let me qualify that. I drop the scope voltage setting down to 10mV/DIV and then picked up some "noisy" signals on the TDI to a p-p of about 30mV. Probably the blaster doing his best to drive the signal to 2V5 or the noise feeding in during the tristated periods.
tdi low and the status pin remains the unsolved mysteries...
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