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Honored Contributor I

JTAG problem with Stratix II GX PCI Express Dev. Board

Dear all,  


I'm using Quartus II 9.0 with the dev. kit in the title. I have no problem with programming the board in standalone mode using the USB Blaster cable, however, when the board is plugged into the PCI Express slot I usually get some JTAG errors ("Can't access JTAG chain", "JTAG chain in use"). The JTAG debugger can usually see the FPGA, sometimes the CPLD too, and sometimes it sees some (or a lot of) non-existent devices in the JTAG chain.  


According to the user guide, it's possible to program the board while plugged into the PC (one needs "the luck of good timing"). The other possibility would be to flash the board in standalone mode, but I only have OpenCore license for the IP cores I use, so I can't generate flash programming files.  


I tried to set all unused pins "as inputs tri-stated" in a simple LED-blinking project, and downloaded it to the FPGA in standalone mode. I don't know why this would change anything after restarting the board (as it reloads the factory code from the flash), but after this I had no problem with programming the board plugged into the PC. This was yesterday evening. This morning it started again, and I can't program the FPGA. 


Any comments, tips, solutions would be greatly appreciated.
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