Functional description

STLBC01

16/40

DocID022984 Rev 2

5

Functional description

5.1

STBLC01 startup

This section describes the STBLC01 startup procedure. The description is intended to be

informational only, as it is independent of any external actions. That application does

however select the preferred communication interface by setting the pin SEL

(a)

(SEL = 1

SPI, SEL = 0 UART).

5.1.1

Startup

When a 3 V battery is connected to the STBLC01, an internal RC oscillator starts up,

providing a clock with fixed duty-cycle to the power check circuit. After the power check

indicates enough voltage on VDD, the Xtal oscillator is enabled and when its startup

procedure is completed, the main logic can use the Xtal clock as reference.

5.1.2

End of the boot-up procedure

Once the XTAL oscillator clock is available to the digital part of the controller, the STBLC01

enters idle state and an event is sent to the host through the selected communication

interface. Refer to

Section 6 for a complete description of how to send commands and read

events from the STBLC01.

At the end of the boot sequence, the STBLC01 returns an event

STBLC_POWER_MODE_IDLE to the host to notify that the system has entered in Idle

mode. If for any reason the first HCI event is corrupted after start-up, for example if the host

needs a long time to initialize or if the SEL signal is not stable at start-up time, it is

recommended that the host generates an additional reset to ensure a proper start-up.

5.2

STBLC01 power modes

The STBLC01 can be configured to work in three main power modes which are

automatically chosen based on the selected chip state described in

Section 5.3. These

modes are, however, not directly selectable by application. For this reason this section is

intended to be informational.

5.2.1

Standby mode

In this mode the Xtal is up and running and is the main clock source of the system. The

internal RC oscillator is active.

5.2.2

Xtreme mode

In Xtreme mode, the Xtal oscillator is turned off but the internal RC is kept on. The supply

voltage of the logic is lowered to reduce the effect of leakage. The complete controller status

is kept.

a.

In order to avoid issues at boot-up due to interface selection, it is advisable to pull up (SPI) or pull down (UART)

the pin SEL with a 10 k

Ω.