SPIRIT1 datasheet(27/94 Pages) STMICROELECTRONICS

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SPIRIT1

Operating modes

Doc ID 022758 Rev 3

27/94

Operating modes

The SPIRIT1 is provided with a built-in main controller which controls the switching between

the two main operating modes: transmit (TX) and receive (RX).

In shutdown condition (the SPIRIT1 can be switched on/off with the external pin SDN, all

other functions/registers/commands are available through the SPI interface and GPIOs), no

internal supply is generated (in order to have minimum battery leakage), and hence, all

stored data and configurations are lost. From shutdown, the SPIRIT1 can be switched on

from the SDN pin and goes into READY state, which is the default, where the reference

signal from XO is available.

From READY state, the SPIRIT1 can be moved to LOCK state to generate the high

precision LO signal and/or TX or RX modes. Switching from RX to TX and vice versa can

happen only by passing through the LOCK state. This operation is normally managed by

radio control with a single user command (TX or RX). At the end of the operations above,

the SPIRIT1 can return to its default state (READY) and can then be put into a sleeping

condition (SLEEP state), having very low power consumption. If no timeout is required, the

SPIRIT1 can be moved from READY to STANDBY state, which has the lowest possible

current consumption while retaining FIFO, status and configuration registers. To manage the

transitions towards and between these operating modes, the controller works as a state-

machine, whose state switching is driven by SPI commands. See Figure 3 for state diagram

and transition time between states.

Figure 3.

Diagram and transition

The SPIRIT1 radio control has three stable states (READY, STANDBY, LOCK) which may be

defined stable, and they are accessed by the specific commands (respectively READY,

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