When operating in high-gain state, the Tau2 core requires a “Long FFC” operation whenever it heats or cools through approximately 0 °C, 40 °C, or 65 °C. For example, long FFC is required if the core is powered on at -10 °C and then is heated to +10 °C. The long FFC operation takes approximately 0.1 sec longer than the normal “short” FFC operation and allows the core to automatically load calibration terms that are appropriate for the current operating temperature range. Additionally, when switching between High Gain and Low Gain mode, a Long FFC must be commanded in order to load the new calibration terms required for the gain switch to complete.
The host system does not need to monitor the above conditions because the Tau has a set of FFC flags that will identify when a Long or Short FFC is needed. When a Long FFC needs to be commanded, the Tau will set either the “Gain switch desired” flag or the “NUC switch desired” flag to 1. A user can query this flag using the READ_SENSOR serial command (0x20).
When the above conditions are not fulfilled, the short FFC should be used to for periodic FFC corrections. Short FFCs should be sent whenever the “FFC desired” flag is set to 1 and a user can query this flag using the READ_SENSOR command (0x20).