Honored ContributorWhen i try to program the FPGA cyclone III i get this error :
error: can't access jtag chain
error: operation failed. I am using a FPGA cyclone III .I would be able to program it a few months ago with no problem but now it suddenly gives me that error.Can anyone help?? ps. I am using the usb blaster. please can somebody help me?
Honored ContributorThere can be a lot of reasons. Power supply, unconnected pin, missing pull-up... You can start with the JTAG chain debugger (described on pages 20-20 to 20-29 of the programmer datasheet (http://www.altera.com/literature/hb/qts/qts_qii53022.pdf)).
Honored ContributorIf you can't access the JTAG chain, the primary reason could be connection problem or no power detected on the JTAG chain. Please check your JTAG header pins (and possibly connections). You might have mistakenly misplaced them.
Honored Contributoryou can also check with your blaster. try changing it and configuring with new blaster. sometimes the buffer inside blaster damages which might cause this error.
Honored Contributorthe same problem is trouble me too，but when i check my quartusII 9.0, i haven't find JTAG debug tools under the tools menu。can anyone help me pls！
Honored ContributorTools > JTAG Debug tools was introduced later in 10.0
Honored ContributorZhang, in Quartus 9.1 the JTAG debugger is not under Tools; it is under Processing->JTAG Chain Debugger. This is the menu of the Programmer tool, not the main Quartus window. Hopefully it is there in 9.0 as well.
I am having the same problem with a custom PCB that I designed and built using a USB Blaster for JTAG communications with a Cyclone III. The design is based on a known-good design, but I have not been able to establish communications with the FPGA yet. Sadly there are many MANY things that can go wrong with such a complex system, resulting in loss of communications.Honored ContributorHI ,the same problem puzzled me now, and i don't know where the wrong is. The pcb is also a finished product,when i download the program by jtag, it gives the error "can't access the jtag chain"
The 50MHZ crystal's output is between 1.2v-2.2v. Whether the source is right?Honored ContributorEven with no clock at all, the FPGA should respond on the JTAG connection. The problem is probably somewhere else that the crystal. Check the power supplies, ground connections, impedances on the JTAG lines, etc... Check also the JTAG signals with a scope, especially the clock that is often the source of JTAG problems.
As for the voltage levels, you can check the input/outputs characteristics of your FPGA in the literature and see if you can use an I/O standard that is compatible with those voltage levels.Honored ContributorHii here is my pcb
http://hiphotos.baidu.com/wswuda2007...5692457e8d.jpg (http://hiphotos.baidu.com/wswuda2007/pic/item/bfae41cbd9c13e5692457e8d.jpg) http://hiphotos.baidu.com/wswuda2007...4501e9288d.jpg (http://hiphotos.baidu.com/wswuda2007/pic/item/598f21c9b4e24f4501e9288d.jpg) http://hiphotos.baidu.com/wswuda2007...d7b2b7dc8d.jpg (http://hiphotos.baidu.com/wswuda2007/pic/item/e08f2341110f9bd7b2b7dc8d.jpg) Is there need anyother connection?Honored Contributor
