State of unused pins in Spartan II.

Hi, What is a state of unused pins in SpartanII device? Is this high impedance state?

Best Regards Krzysztof Przednowek

Reply to
Krzysztof Przednowek
Loading thread data ...

The unused pins can be high impedance, but the actual state depends on the configuration options when you build the .bit file.

The default is weak pull-down. If you're using ISE, right click on "Generate Programming File" in the process view and select "properties". In the Configuration Options tab you'll find "Unused IOB Pins" where you can select pullup, pulldown or float (high Z).

The state of IOB pins during configuration is determined by the mode pins on Spartan II. You have the choice of high Z or pullup.

While the pullup or pulldown is referred to as "weak" in the documents, it's been my experience that it is stong enough to affect connected nets, especially where you have other devices with "weak" pullup or pulldown. For example many chips have dual purpose pins that double as configuration during reset and have internal pullup or pulldown for the default strapping value. The "weak" pullup/pulldown in Spartan II is often strong enough to overcome these internal pullup or pulldowns and change the default configuration options. For nets like this you need to consider both the post configuration options in ISE and the mode selects for pre-configuration.

Also be aware that "Unused" refers to the post map IOB list which may have some extra unused p> Hi,

Reply to

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.