SI4455-C2A-GMR Datasheet, PDF (28/39 Pages) Silicon Laboratories – EASY-TO-USE, LOW-CURRENT OOK/(G)FSK SUB-GHZ TRANSCEIVER, TRANSMITTER, AND RECEIVER

Si4x55-C
5.2.6. TX State
The TX state is used whenever the device is required to transmit data. It is entered using either the START_TX or
CHANGE_STATE command. With the START_TX command, the next state can be defined to insure optimal
timing. When either command is sent to enter TX state, an internal sequencer automatically takes care of all
actions required to move between states with no additional user commands needed. Examples of the timing of this
transition can be seen in Figure 14 and Figure 15. The specific sequencer controlled events that take place during
this time can include enable internal LDOs, start up crystal oscillator, enable PLL, calibrate VCO/PLL, active power
amplifier, and transmit packet.
Figure 17 shows an example of the commands and timing for the START_TX command. CTS will go high as soon
as the sequencer puts the part into TX state. As the sequencer is stepping through the events listed above, CTS
will be low and no new commands or property changes are allowed. If the nIRQ is used to monitor the current
state, there will be a slight delay caused by the internal hardware from when the event actually occurs to when the
transition occurs on the nIRQ. The time from entering TX state to when the nIRQ will transition is 13 µs. If a GPIO
is programmed for TX state or used as control for a transmit/receive switch (TR switch), there is no delay.
CTS
nSEL
SDI
Current State
FRR
nIRQ
GPIO-TX State
START_TX
Initial State
Initial State
TX State
TX State
TXCOMPLETE_STATE
TXCOMPLETE_STATE
Figure 17. START_TX Commands and Timing
5.2.7. RX State
The RX state is used whenever the device is required to receive data. It is entered using either the START_RX or
CHANGE_STATE commands. With the START_RX command, the next state can be defined to insure optimal
timing. When either command is sent to enter RX state, an internal sequencer automatically takes care of all
actions required to move between states with no additional user commands needed. The sequencer controlled
events can include enable the digital and analog LDOs, start up the crystal oscillator, enable PLL, calibrate VCO,
enable receiver circuits, and enable receive mode. The device will also automatically set up all receiver features
such as packet handling based upon the initial configuration of the device.
28
Rev 1.0