User's Manual

SPSGRFC
P a g e | 4 Rev 0.1
4 Short description of the module functional behaviour
The SPIRIT1 device inside the SPSGRFC module 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 SPSGRFC module 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.
The GPIO and SPI ports of the module during SHUTDOWN are in HiZ. From shutdown state, the SPSGRFC
module 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 SPSGRFC module 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 SPSGRFC module 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 SPSGRFC 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, whose
state switching is driven by SPI commands.
Figure 2 - Module functional states transitions diagram