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Altera_Forum
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10 years ago

Cyclone IV configuration - nCONFIG signal and JTAG programming issue

Hi, I have a custom board for EP4CE22E22 Cyclone IV FPGA. I have configured the board for JTAG only mode and using USB Blaster Rev.B for programming. The problem I am facing is that JTAG Scan f...
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Altera_Forum
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10 years ago

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