AR# 3404

描述

What happens to unused pins in XC9500/XL/XV designs? Do I need to tie them to ground on the board?

解决方案

Unused pins in XC9500 devices are left floating unless you create programmable ground pins with the fitter option (see below). This option directs the fitter to tie unused pins to ground internally, so that you do not have to tie these pins to ground on your board. Tying unused I/O to ground either on the board or via software is recommended, as it reduces noise and power consumption from floating signals.

Foundation ISE

To create programmable ground pins on unused I/O, follow these steps:

1. In the Foundation ISE Project Navigator, right-click on "Implement Design" in the Processes window.

2. Select "Properties."

3. In the Basic tab, select the "Create Programmable GND pins on Unused I/O" option.

Foundation Classic

To create programmable ground pins on unused I/O, follow these steps:

1. In the Foundation Project Manager, the options are located under "Implementation -> Options." Select the "User-Defined" option.

2. Click on "Edit Options" and select the Basic tab.

3. Select the "Create Programmable GND pins on Unused I/O" option.

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