cs5535 National Semiconductor Corporation, cs5535 Datasheet - Page 152

• Manufacturer Part Number: cs5535
• Description: Geode Cs5535 Companion Multi-function South Bridge
• Manufacturer: National Semiconductor Corporation

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GPIO Subsystem Functional Description
4.15.5.6 Auto Sense
Two GPIOs (GPIO5 and GPIO6) have a function called
“Auto-sense”. Auto-sense is a method of automatically
determining whether or not to apply a pull-up or pull-down
to the corresponding GPIO input.
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Auto-sensed inputs behave as follows: when reset is
applied to the system, a weak pull-up is applied to the pad.
When reset is de-asserted, the sensed value is used to
establish the pull-up/down state on the de-assertion edge.
If nothing pulls down the pad, then the pull-up continues to
be applied. If the pad is pulled down, then the pull-up is
cleared to 0 and the pull-down is set to 1. If a pull-down is
desired, a diode between the reset signal and the GPIO pin
will pull it down during the Auto-Sense operation but have
no effect during normal operation.
Revision 0.8