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AR# 6352

4.1i FPGA Editor - How do I activate pull-downs on unused pins?

Description

Keywords: 4000, Spartan, pull-down, pulldown, unused, I/O, IO, pin, implementation, configuration, options, FPGA, Editor

Urgency: Standard

General Description:
How can I activate the pull-downs on the unused I/O pins, as they are pulled up, by default, with an internal pull-up resistor (20k-100k ohms)?

Solution

The Xilinx implementation tools do not yet offer the user the option of globally activating the internal pull-downs on unused I/O. However, this task can be accomplished with the help of FPGA Editor.

Follow these steps:

1. Open your placed and routed design in FPGA Editor (<design_name>.ncd)

2. Set the Edit Mode. (Go to File -> Main Properties, and set Edit Mode to "Read Write".)

3. Highlight an unused IOB and select "Add" (on the right side). This adds the IOB to your design -- you can give it any name you like.

4. Once you've added the IOB, it should appear in blue. Double-click on it to see the internals of the IOB. To make changes, you'll have to click the second-from-left button (looks like a pencil) to allow editing.

5. Click the check box next to "Pull-down".

6. To apply the edits, click the second-from-right button (looks like an arrow and small window).

7. Save the design by selecting File -> Save.
AR# 6352
Date Created 05/03/1999
Last Updated 10/08/2003
Status Archive
Type General Article