Answers Database

XC9500: How are unused I/O pins handled?


Record #1536

Product Family:  Hardware

Product Line:  9500

Problem Title:
XC9500:	How are unused I/O pins handled?


Problem Description:
Keywords: 9500, unused pins, I/Os, ground bounce, noise, programmable ground

Urgency: standard

General Description: How to handle unused pins of a XC9500 device?


Solution 1:

Xilinx recommends tying any unused pins to either the board ground or to a
board trace. This will help reduce problems associated with ground bounce and
noise.

With the XACT-CPLD 6.x software tools, unused I/O pins in the XC9500 devices
are left floating.

However, with the M1.x software. there is a "Create Programmable Ground Pins"
option in the Basic tab of XC9500 Implementation Options template. To get
there from the Design Manager, start Flow Engine. Go to Setup -> Options and
select the button marked Edit Template. You can select this option by clicking
on the radio button.

If this option is selected in addition to tying the unused pins to ground,
it will be more beneficial as far as noise and ground bounce issues are
concerned.




End of Record #1536