PUDC_B管脚用途

Pull-Up During Configuration (bar) Active-Low PUDC_B input enables internal pull-up resistors on the SelectIO pins after power-up and during configuration.

• When PUDC_B is Low, internal pull-up resistors are enabled on each SelectIO pin.

• When PUDC_B is High, internal pull-up resistors are disabled on each SelectIO pin.

PUDC_B must be tied either directly, or via a ≤ 1kΩ to VCCO_14 or GND.

Caution! Do not allow this pin to float before and during configuration.

参考文献：

https://www.xilinx.com/support/documentation/user_guides/ug470_7Series_Config.pdf

http://china.xilinx.com/support/answers/50802.html

http://blog.csdn.net/techexchangeischeap/article/details/72698529 

Xilinx 7 Serial PUDC_B