板子仿真时，出现以下错误·，在查手册时发现，问题可能是JTAG的管脚与地短路，但是测量时，并未短路。那么主要原因可能是什么呢？
Error connecting to the target:
(Error -233 @ 0x0)
The JTAG IR and DR scan-paths cannot circulate bits, they may be broken.
An attempt to scan the JTAG scan-path has failed.
The target's JTAG scan-path appears to be broken
with a stuck-at-ones or stuck-at-zero fault.
(Emulation package 9.1.0.00001)
