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AR# 8458

CPLD CoolRunner-II XPLA3 - To what state are unused I/O pins set?

Description

To what state are unused I/O pins set?

解决方案

XPLA3

Unused I/O pins should always be terminated on the board to reduce current and minimize noise.

5.x and newer design tools

Unused I/O pins will be pulled up internally by default. You can disable this by selecting "Float" under "Unused Pin Termination" in the design tools.

4.1i design tools

Unused I/O pins will be pulled up internally by default. You can disable this by deselecting "Pull Up Unused I/O Pins" in the design tools. (This is found under the "Generate Programming File" properties.)

For other common questions, refer to the CPLD FAQ: (Xilinx Answer 24167).

CoolRunner-II

Unused I/O pins should always be terminated to minimize leakage current and noise.

5.x and newer design tools

Unused I/O pins will be terminated with a bus-hold "keeper" circuit by default. You can change this by selecting "Float", "Pullup", or "Ground" under "Unused Pin Termination" option in the design tools.

- If you select "Float", unused I/Os will be left floating; you must terminate these pins externally.

- If you select "Pullup", unused I/Os will be internally pulled up. You can then choose to either leave these pins floating on the board or to ground them.

- If you select "Ground", all unused I/Os will be internally grounded. You can then choose to either leave these pins floating on the board or to ground them.

For other common CPLD questions, refer to the CPLD FAQ: (Xilinx Answer 24167).

AR# 8458
创建日期 08/21/2007
Last Updated 12/15/2012
状态 Active
Type 综合文章