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在使用openocd调试过程中，JTAG scan chain interrogation failed: all ones/zero是最常见的一种问题了，很多对嵌入式开发或openocd不了解的同学都深受困扰。openocd完整输出信息如下：
Nuclei OpenOCD, 64-bit Open On-Chip Debugger 0.10.0+dev-00036-gbfc178ffb (2021-02-01-06:41)
Licensed under GNU GPL v2
For bug reports, read
http://openocd.org/doc/doxygen/bugs.html
Info : libusb_open() failed with LIBUSB_ERROR_NOT_FOUND
Info : no device found, trying D2xx driver
Info : D2xx device count: 2
Info : Connecting to "(null)" using D2xx mode...
Info : clock speed 1000 kHz
Error: JTAG scan chain interrogation failed: all ones
Error: Check JTAG interface, timings, target power, etc.
Error: Trying to use configured scan chain anyway...
Error: riscv.cpu: IR capture error; saw 0x1f not 0x01
Warn : Bypassing JTAG setup events due to errors
Error: Unsupported DTM version: 15
Info : Listening on port 3333 for gdb connections
Error: Target not examined yet
Error: Unsupported DTM version: 15
出现这个错误信息，不代表所有的东西都有问题，下面这些部分可以确定是没有问题的
openocd启动正常
openocd脚本没有错误
驱动没有问题
调试器被正确识别
JTAG接口没有正确连接/部分线断开
IO约束中缺少set_property KEEPER true [get_ports mcu_TMS]
