1）JTAG 下载bit文件，FPGA正常启动。
2）下载mcs文件到外部flash，然后重新上电，（插着JTAG，刚开始没把稳这个差异）涌现加载不堪利的征象。
3) 让硬件同事，帮忙先烧后贴FLASH，创造FPGA起来了。
比拟了下FLASH先烧后贴与直接下载mcs文件的差异，创造文件是没有差异的。
这就奇怪了？ 咋就起不来了？
有光阴，把下载mcs文件的板子，拿到同事工位，上电，创造起来了。？？？这是什么鬼。
比拟了下差异，只是少插了个JTAG。
利用JATG读取了上电失落败时，FPGA启动寄存器干系信息，如下：
正常启动的FPGA，状态寄存器如下：
差异已用箭头标出。
config_status并未显示任何缺点，指示加载卡在了phase 0，如下图所示
这个问题就很困恼了？ 这个插着JTAG咋就起不来了呢？
去xilinx网上找了类似问题：
有个解答觉得很不错
https://forums.xilinx.com/t5/Vivado/在JTAG下载器连接时FPGA不加载flash里的程序/td-p/991746
xilinx官方答案如下：
https://www.xilinx.com/support/answers/66954.html
问题办理方案
搬运下XLINX的办理方案
SolutionThe issue could occur under three conditions:Device power on or power cycle. Pulsing PROGRAM_B does not result in this issue because the Vivado Hardware Manager does not see a cable disconnection and perform the cable auto detection.User issues "refresh_hw_devices" commandUser plugs in the JTAG cablePotential Work-arounds include the following:1) Set the following parameter to disable the power up detectionset_param labtools.auto_update_hardware 0Note: You need to create a Vivado_init.tcl script and add the above parameter in it.Additional information on Vivado_init.tcl:When you start the Xilinx Design tools, it looks for the Vivado_init.tcl initialization script in two different locations:1) In the software installation: installdir/Vivado/version/scripts/Vivado_init.tclinstalldir is the installation directory where the Vivado Design Suite is installed.2) In the local user directory:For Windows 7: %APPDATA%/Roaming/Xilinx/Vivado/Vivado_init.tclFor Linux: $HOME/.Xilinx/Vivado/Vivado_init.tclIf Vivado_init.tcl exists in both of these locations, Vivado sources the file from the installation directory first, and then from your home directory.For more information, see the Loading and Running Tcl Scripts chapter in (UG894) Vivado Design Suite User Guide Using Tcl Scripting.http://www.xilinx.com/cgi-bin/docs/rdoc?v=latest;d=ug894-vivado-tcl-scripting.pdf2) Unplug the cable prior to power up or power cycle.3) Slow down occurrence of the polling.For example to poll once an hour, launch hw_server with the following option:hw_server -e "set jtag-poll-delay 3600000000"This command should be called in the CMD window instead of Vivado Tcl console.4) Close and reopen the target in JTAG mode as follows to prevent any polling from happening, then restore back to normal mode:a) Close and reopen the target in JTAG mode:set tmp_target [ get_hw_targets -filter { IS_OPENED == 1 }]close_hw_target $tmp_targetopen_hw_target -jtag_mode on $tmp_targetset_property LOCK true [get_property HW_JTAG $tmp_target]b) Restore back to normal mode once the part has booted:set_property LOCK false [get_property HW_JTAG $tmp_targetclose_hw_target $tmp_targetopen_hw_target $tmp_target总结和建议
实际运用碰着的问题，很多还是能在XLINX上找到办理办法的。
