SPIRIT1 Datasheet, PDF (27/94 Pages) STMicroelectronics – Low data rate, low power sub-1GHZ transceiver

SPIRIT1
7
Operating modes
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
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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,
Doc ID 022758 Rev 3
27/94