Altera USB Blaster JTAG problem: Suddenly unable to connect to FPGA

[Altera_Forum]

Hi 

 I'm using a custom Cyclone V board which I've been using for several days through the Altera USB Blaster with no problems. Suddenly, the Blaster is unable to connect to the board. The blaster is OK because is properly working with other boards, but it fails with the first one. FPGA looks is ok because during start-up, the loaded bitstream turns on and turns off several leds according to the expected behaviour. But USB Blaster still unable to connect.  Today, a second board has started to fail as the first one.  Whats going wrong? I've found several threads where people suggest to load 3.8V or 5V directly on the TDO pins for several seconds in order to blow up a protection. I've tried this with no success.   The jtagconfig -d output shows this message:  $ jtagconfig -d 1) USB-Blaster [USB-0]  Unable to read device chain - JTAG chain broken   Captured DR after reset = (02B050DD)  Captured IR after reset = ()  Captured Bypass after reset = (0)  Captured Bypass chain = ()   What could I do? Any suggestion?  Thanks in advance.  Regards,  Eduardo

[Altera_Forum]

--- Quote Start ---   Today, a second board has started to fail as the first one.  Whats going wrong? I've found several threads where people suggest to load 3.8V or 5V directly on the TDO pins for several seconds in order to blow up a protection. I've tried this with no success.      --- Quote End ---    Hi Eduardo.   Applying 3.8 to 5V on the TDO line sounds like a method of destroying the TDO.. I would definitly not due this.  What is the VCCIO of the bank with the JTAG lines. If it's 3.3 V, you may have enough overshoot that you are killing the FPGA pins due to overshoot/undershoot unless you have external clamp diodes installed.  I haven't see this issue, but I have seen issues when the VCC of the USB Blaster connector is too high. Check the Cyclone V handbook, and see if this is the issue.  I have also seen issues due to poor TCK termination on the board. I adjusted one of my USB blasters by switching the 10 ohm source termination resistor with a 33 ohm source termination resistor.  Pete

[Altera_Forum]

Based on the observation, seems like there might be some power related issue with your boards as you have second board starts to fail after the first. It is recommended for you to look into your boards to see if there is any power issue. You can also counter check your on board power pin connection with reference to the pin connection guidelines to avoid further damaging other good boards.

[Altera_Forum]

Check out this link to the Cyclone V pin connection guideline document: 

https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/dp/cyclone-v/pcg-01014.pdf

[Altera_Forum]

Hi guys. 

 I got new usb blaster 2 it works properly while programming old max|| Pld via Jtag Chain. But i can't use it to download pof file via active serial toward an epc16 device. I get " Current programming hardware does not support active serial".   I'm new to the forum and Fpga use, can some one help me to get out this issue?  Thanks in advance  Alfredo.