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Design >> High-Speed I/O Design >> Weak pull up/down and keeper in IOs
https://designers-guide.org/forum/YaBB.pl?num=1407850073

Message started by dewy on Aug 12^th, 2014, 6:27am

Title: Weak pull up/down and keeper in IOs
Post by dewy on Aug 12^th, 2014, 6:27am

Hi,

The block mentioned in the subject is usually used in IOs to pull up/down the pad when it is floating (please correct if this is wrong). Besides these, there is also a keeper mode and I am not sure when that is enabled. Can anyone give me an explanation on when exactly each of the mode (up/down/keeper) is enabled?

Title: Re: Weak pull up/down and keeper in IOs
Post by loose-electron on Aug 12^th, 2014, 11:48am

Can be unique to the particular device.

Most of the time it means some form of pull up, or pull down (if driver to the pin is tristate it fgoes to that state) or a "keeper" which means that the input is weakly held in a particular state, such that nothing is connected outside the IC but the pin is kept either high or low.

The details are unique to a device. If you look at a FPGA/CPLD/uController document, these definable states will have explicit definitions. (i.e. "5 uA pull up current is turned on when the I/O is configured in the Keep High mode)

unique to vendor-design

RTFM