JTAG连不上，什么原因呀

[Labtools 27-2269] No devices detected on target localhost:3121/xilinx_tcf/Digilent/210251A08870.
Check cable connectivity and that the target board is powered up then
use the disconnect_hw_server and connect_hw_server to re-register this hardware target.

请参考这个，看下能否解决 https://www.uisrc.com/t-1692.html