Standby mode is the first operational mode where the controller can interact with the SBC. Most features are accessible in this mode except transmission from wired transceivers. Standby mode is where most of the configuration of the device takes place as this is the first mode in which the SPI bus becomes active. Upon entry into standby mode a long window watchdog timer starts and must be triggered through the SPI bus or else the device can transition back to reset mode – this can be avoided during prototyping by holding the SW pin in the active state (by default the active state is high).

There are three different ways to enter into the standby mode. The first way is the transition from restart mode to standby when VCC1 has surpassed the UVCC1_R threshold and remained over the threshold for t_RSTN_act. If the SPI bus is active a SPI command can always be used to transition device back into standby mode – this is applicable for when device is in normal mode or sleep mode (if VCC1 is active in sleep, which by default is not). A soft reset can also cause the device to return to standby mode – but soft resets also require the SPI bus to be active.

There are multiple ways to leave standby mode – but the ways can be categorized in two groups: SPI command or fault condition. If everything is working as intended to leave standby mode a SPI command needs to be initiated and can lead the device into normal mode or sleep mode depending on specific command issued. The other exit path from standby is due to a fault condition – which depending on fault type and device configuration can result in the device entering restart mode, sleep mode, or fail-safe mode.

Figure 2-4 Standby Mode