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You shouldn't have nSTATUS high without nCONFIG high. It's your responsibility to 'drive' nCONFIG. This could well amount to a simple pull-up resistor. I'd suggest you either have a manufacturing fault or one (or more) of your power pins are not powered. Check them all.
The JTAG will not work unless nCONFIG is high.
Yes, you should power your USB-Blaster from VCCA (2.5V). However, this is a common design fault that is not likely to be, or cause you, a problem. I do recommend you correct it, by modifying your board, and certainly if you re-spin the board.
If connected for JTAG only you should also ensure DCLK and DATA0 are drive high or low (whichever is convenient), don't leave them floating.
Refer to Table 8-20 on page 8-64 of the
configuration and remote system upgrades in cyclone iv devices (
https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/hb/cyclone-iv/cyiv-51008.pdf) for an explanation of the relevant configuration pins. Also note the behavior of nCONFIG and nSTATUS in any of the 'Configuration Timing Waveform' figures.
Cheers,
Alex
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Hi Alex,
Yes, in my design both nCONFIG & nSTATUS are pulled high by a 10K resistor to VCCIO. You can see in the latest attachment that both nSTATUS (A4) and nCONFIG (A5) signals are high during JTAG scan. It was unconnected E-pad that was causing nConfig to go LOW.
I forgot to mention, both DCLK and DATA0 are also tied to VCCIO. I have also tried to perform JTAG scan with 2.5V on Pin.4 of JTAG connector (Powering USB Blaster) but TDO remains stuck at High.
Honored Contributor
