dft扫描测试中set_dft_signal求助！！！

eda—wdy

在一个脚本看到，为什么下面的scanenable信号和scanmode信号-view既要spec又要existing呢 不是一个已有结构的信号或者扫描链定义的信号吗？为什么下面这两个都要定义？
set_dft_signal -view spec         -type ScanEnable  -port scan_enable -active_state 1
set_dft_signal -view existing_dft -type ScanEnable  -port scan_enable -active_state 1
set_dft_signal -view spec         -type Constant    -port scan_mode   -active_state 1
set_dft_signal -view existing_dft -type Constant    -port scan_mode   -active_state 1

greatao

In some cases, you might need to define a signal twice, once with -view existing_dft and once with -view spec. This can occur when you have manually routed a signal to some design logic, but you also require the insert_dft command to make its own connections. For example, you might connect the scan enable signal to some top-level DFT logic contained in the RTL, but you also need the scan enable signal connected to the scan flip-flops:

set_dft_signal -view existing_dft -type ScanEnable -port MY_SCAN_EN
set_dft_signal -view spec -type ScanEnable -port MY_SCAN_EN


以上引用自solvnet。