The first mode is a transitory mode, meaning that this operating state is transient and the SBC does not remain in this mode for long and can automatically transition out of this mode when operating conditions permit this to do so. The first state is the init mode – or initialization mode – which is used for the device to initialize. This mode is short lived and the operator, nor a controller, can do anything with SBC during this mode. Most subsystems are still off in the init mode with the exception of VCC1 and VCC2 which are turned on and ramping towards the regulated voltage targets (3.3V or 5V for VCC1 and 5V for VCC2)

There are four ways to enter this state and one way to exit. The most common way to enter init mode is to turn the power onto the device – as soon as the VSUP pin has reached appropriate power levels, VSUP_(PU)R, the device can enter init mode. A power on reset (POR) can also cause the device to become unpowered and reinitialize in init mode. A hard reset or an input signal placed on nRST can also cause the device to switch back to init mode, however in these two last cases the VSUP pin is already at an adequate voltage to begin initialization. The SBC can exit Init mode when VSUP crosses the UVSUP_R threshold and then enters into restart mode.

Figure 2-2 Init Mode