Cold boot mode is used to heat-up a system by turning on cold boot rails for certain amounts of time when it is under an extreme code temperature. UCD device is communicated with the system via particular GPI (thermal state GPI) which is output from a thermal device. Cold boot mode is only entering once per UCD reset. There is no system watch dog Reset during the cold boot mode.

Device reads the thermal state GPI to determine whether it should start cold boot or not when it is out of reset. When the input of thermal state GPI is DE-ASSERTED, device enters cold boot mode and log the GPI fault if the GPI fault log enable bit is set, otherwise device enters normal mode. The following changes on the thermal state GPI do not introduce any logging. Only one GPI can be assigned for this function and one it is assigned, it cannot be used for any other GPI functions.

The rails used in the cold boot mode are configurable. For those rails with Sequence On Dependency on the thermal state GPI, they (non-cold boot rails) are not powered-up during the cold boot since the dependency is not met. But non-cold boot rails will be power-on under normal mode since thermal state GPI is treated as ASSERTED when cold boot mode is over. For those rails without sequence on dependency on the thermal state GPI, they (cold boot rails) are power-on under both cold boot and normal mode. It is application’s responsibility to set the proper ON_OFF_CONFIG for those cold boot rails. Cold boot rails are not power-on if their ON_OFF_CONFIG settings are not met under cold boot mode. Cold boot mode timeout is used to tell how long the device shall stay at the cold boot before it stops monitoring the thermal state GPI and shutdown all cold boot rails with EN control. Normal Boot Start Delay is used to tell how long device should wait to ramp up the powers after all cold boot rails with EN are below POWER_GOOD_OFF.

- If system temperature is < threshold degree C (Thermal State GPI)
        o   Yes(DE_ASSERTED):
            § Log GPI fault 
            § Start Cold Boot Timeout 
            § No System Watchdog output
            § Ramp up the power supplies based on ON_OFF_CONFIG   
            § Wait for thermal state GPI ASSERTED OR “Cold Boot Mode Timeout expired”
            § Disable the thermostat input listening mode
            § Force to shutdown down all cold boot rails with EN control immediately
            § Wait all cold boot rails with EN control below POWER_GOOD_OFF
            § Start and Wait “Normal boot Start Delay expired”
- Disable the thermostat input listening mode
- Treated Thermal State GPI as ASSERTED
- Ramp up power supplies based on ON_OFF_CONFIG