7.4.9 GPO Delays

The GPOs can be configured so that they manifest a change in logic with a delay on assertion, deassertion, both or none. GPO behavior using delays will have different effects depending if the logic change occurs at a faster rate than the delay. On a normal delay configuration, if the logic for a GPO changes to a state and reverts back to previous state within the time of a delay then the GPO will not manifest the change of state on the pin. In Figure 20 the GPO is set so that it follows the GPI with a 3ms delay at assertion and also at de-assertion. When the GPI first changes to high logic state, the state is maintained for a time longer than the delay allowing the GPO to follow with appropriate logic state. The same goes for when the GPI returns to its previous low logic state. The second time that the GPI changes to a high logic state it retuns to low logic state before the delay time expires. In this case the GPO does not change state. A delay configured in this manner serves as a glitch filter for the GPO.

Figure 20. GPO Behavior When Not Ignoring Inputs During Delay

The Ignore Input During Delay bit allows to output a change in GPO even if it occurs for a time shorter than the delay. This configuration setting has the GPO ignore any activity from the triggering event until the delay expires. Figure 21 represents the two cases for when ignoring the inputs during a delay. In the case in which the logic changes occur with more time than the delay, the GPO signal looks the same as if the input was not ignored. Then on a GPI pulse shorter than the delay the GPO still changes state. Any pulse that occurs on the GPO when having the Ignore Input During Delay bit set will have a width of at least the time delay.

Figure 21. GPO Behavior When Ignoring Inputs During Delay