# Timing

The RSL15 system performs a number of steps, following resets and on transitions to or from various power modes, to ensure that when entering into Run Mode the user application can properly use and configure (or reconfigure) various system components needed by the application.

The following sub-sections discuss system timing for system startup (following a power-on reset), as well as for entering and exiting Sleep and Standby Modes.

## Startup Timing

Startup timing starts when a supply voltage is provided to the battery supply voltage (VBAT) and Digital Output Supply Voltage (VDDO). For more information on these power supply inputs, see Section 1.1 “Power Supply Inputs ” on page 1.

A diagram showing the startup timing until the system reaches Run Mode is shown in the "Startup Timing" figure.

Figure: Startup Timing

Timing until a user application starts executes will differ from this diagram for a number of reasons, including:

- If the system is starting up following a full reset, delays awaiting the charging and rise of VBAT, VDDACS, and VREF can be omitted if the system power has remained stable leading up to the reset.

  NOTE: Charging of power supplies at startup can vary significantly, depending on the current and voltage of the supply provided and existing power supply state. To accommodate the worst case startup timing, the "Startup Timing" figure shows the expected worst case timing until nRESET is released.

- For devices executing in a secure state, there is additional startup time in Run Mode for the execution of the Program ROM and potentially a secure bootloader. This additionally needs to account for:
  - Key certificates
  - Content certificates
  - Debug certificates
  - Application authentication, loading, and/or decryption.

For more information about operation in secure modes, see the Security User’s Guide. For more information on the example secure bootloader provided, see the Secure Bootloader Guide guide.

## Sleep Power Mode Related Timing

A diagram providing the timing between when a device in Sleep Mode receives a wakeup event and when the system reaches Run Mode again is shown in Sleep Mode and Wakeup From Sleep Mode Timing (figure).

Figure: Sleep Mode and Wakeup From Sleep Mode Timing

The "Sleep Mode and Wakeup From Sleep Mode Timing" figure includes all expected delays in the wakeup configuration for Sleep Mode. Wakeup timing can vary from the timing shown for a number of different reasons, including:

- Variations in Sleep Mode configuration, as discussed in Power Modes. Elements that are not disabled in a specific Sleep Mode configuration do not require delays during wakeup.

- The desired wakeup delay as controlled by the nRESET delay clock, and configured in the ACS_WAKEUP_CFG_DELAY field of the ACS_WAKEUP_CFG register.

An example current capture from a sample application showing power consumption of the RSL15 device relative to the wakeup timing is provided in the "Example wakeup, Bluetooth advertisement, return to Sleep Mode" figure. This sample application shows a wakeup from Sleep Mode due to an event (at m1), transmits a Bluetooth Low Energy advertisement without receiving a response once in Run Mode, and returns to Sleep Mode (at m2).

Figure: Example wakeup, Bluetooth advertisement, return to Sleep Mode

## Standby Power Mode Related Timing

A diagram providing the timing between when a device in Standby Mode receives a wakeup event and when the system reaches Run Mode again is shown in the "Standby Mode and Wakeup From Standby Mode Timing" figure.

Figure: Standby Mode and Wakeup From Standby Mode Timing

The "Standby Mode and Wakeup From Standby Mode Timing" figure includes all expected delays in the wakeup configuration for Standy Mode. Since most of the critical items remain active in Standby Mode, wakeup timing in Standby Mode is largely determined by the configured wakeup delay. This delay can by configured by adjusting the nRESET delay clock that controls the wakeup delay configuration using the ACS_WAKEUP_CFG_DELAY field of the ACS_WAKEUP_CFG register.