JAJSH44C April 2011 – March 2019 UCD90120A
This feature allows with the use of up to 3 GPIs to enable and disable any rail. This is useful for implementing system low-power modes and the Advanced Configuration and Power Interface (ACPI) specification that is used for operating system directed power management in servers and PCs. In up to 8 system states, the power system designer can define which rails are on and which rails are off. If a new state is presented on the input pins, and a rail is required to change state, it will do so with regard to its sequence-on or sequence-off dependencies.
The OPERATION command is modified when this function causes a rail to change its state. This means that the ON_OFF_CONFIG for a given rail must be set to use the OPERATION command for this function to have any effect on the rail state. The first 3 pins configured with the GPI_CONFIG command are used to select 1 of 8 system states. Whenever the device is reset, these pins are sampled and the system state, if enabled, will be used to update each rail state. When selecting a new system state, changes to the status of the GPIs must not take longer than 1 microsecond. See the UCD90xxx Sequencer and System Health Controller PMBus Command Reference for complete configuration settings of PIN_SELECTED_RAIL_STATES.
|GPI 2 STATE||GPI 1 STATE||GPI 0 STATE||SYSTEM STATE|
|NOT Asserted||NOT Asserted||NOT Asserted||0|
|NOT Asserted||NOT Asserted||Asserted||1|
|NOT Asserted||Asserted||NOT Asserted||2|
|Asserted||NOT Asserted||NOT Asserted||4|