SPSGRF module functional behavior SPSGRF
4/23 DocID027664 Rev 5
2 SPSGRF module functional behavior
The SPIRIT1 device in the SPSGRF module is equipped 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 SPSGRF module can be switched on/off with the external SDN
pin; all other functions/registers/commands are available through the SPI interface and
GPIOs. No internal supply is generated (in order to minimize battery leakage), and therefore
all stored data and configurations are lost.
The GPIO and SPI ports of the module during shutdown are in HiZ. From the SHUTDOWN
state, the SPSGRF module can be switched on from the SDN pin and goes into a READY
state, which is the default, where the reference signal from XO is available.
From the READY state, the SPSGRF module can be moved to a LOCK state to generate
the high precision LO signal and/or TX or RX modes. Switching from RX to TX and vice-
versa can occur 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 events above, the SPSGRF module can return to its default state (READY)
and can then be put into a sleep condition (SLEEP state), characterized by very low power
consumption.
If no timeout is required, the SPSGRF module 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, the state switching of which is driven by SPI
commands.
Figure 2. Module functional state transitions diagram
