SI4455 Datasheet, PDF (24/40 Pages) Silicon Laboratories – 20-Pin 3x3 mm QFN package

Si4455
5.2. Operating Modes and Timing
The primary states of the Si4455 are shown in Figure 11. The shutdown state completely shuts down the radio,
minimizing current consumption and is controlled using the SDN (pin 2). All other states are controlled using the
API commands START_RX, START_TX and CHANGE_STATE. Table 12 shows each of the operating modes with
the time required to reach either RX or TX state as well as the current consumption of each state. The times in
Table 12 are measured from the rising edge of nSEL until the chip is in the desired state. This information is
included for reference only since an automatic sequencer moves the chip from one state to another and so it is not
necessary to manually step through each state. Figure 12 and Figure 13 demonstrate this timing and the current
consumption for each radio state as the chip moves from shutdown or standby to TX and back. Most applications
will utilize the standby mode since this provides the fastest transition response time, maintains all register values,
and results in nearly the same current consumption as shutdown.
Shutdown
SPI Active
Standby
Config
Ready
Tx Tune
Rx Tune
Tx
Rx
Figure 11. State Machine Diagram
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Rev 1.1