SI4464 datasheet(22/56 Pages) SILABS

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Si4464/63/61/60

Rev 1.2

3. Enable PLL.

4. Calibrate VCO/PLL.

5. Wait until PLL settles to required transmit frequency (controlled by an internal timer).

6. Activate power amplifier and wait until power ramping is completed (controlled by an internal timer).

7. Transmit packet.

Steps in this sequence may be eliminated depending on which state the chip is configured to prior to commanding

to TX. By default, the VCO and PLL are calibrated every time the PLL is enabled. When the START_TX API

command is utilized the next state may be defined to ensure optimal timing and turnaround.

Figure 8 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 Fast Response (FRR) or nIRQ is used to

monitor the current state there will be slight delay caused by the internal hardware from when the event actually

occurs to when the transition occurs on the FRR or nIRQ. The time from entering TX state to when the FRR will

update is 5 µs and the time 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.

Figure 8. Start_TX Commands and Timing

3.3.8. RX State

The RX state may be entered from any of the other states by using the “Start RX” or “Change State” API command.

A built-in sequencer takes care of all the actions required to transition between states. The following sequence of

events will occur automatically to get the chip into RX mode when going from standby to RX state:

1. Enable the digital LDO and the analog LDOs.

2. Start up crystal oscillator and wait until ready (controlled by an internal timer).

3. Enable PLL.

4. Calibrate VCO

5. Wait until PLL settles to required receive frequency (controlled by an internal timer).

6. Enable receiver circuits: LNA, mixers, and ADC.

7. Enable receive mode in the digital modem.

Depending on the configuration of the radio, all or some of the following functions will be performed automatically

by the digital modem: AGC, AFC (optional), update status registers, bit synchronization, packet handling (optional)

including sync word, header check, and CRC. Similar to the TX state, the next state after RX may be defined in the

“Start RX” API command. The START_RX commands and timing will be equivalent to the timing shown in Figure 8.

START_TX

CTS

NSEL

SDI

YYY State

Current State

Tx State

nIRQ

YYY State

FRR

Tx State

TXCOMPLETE_STATE

GPIOx – TX state

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