LLCC68 datasheet(71/111 Pages) SEMTECH

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LLCC68

Data Sheet

Rev. 1.1

DS.LLCC68.W.APP

Dec 2024

71 of 111

Semtech

LLCC68

www.semtech.com

13.1.7 SetRxDutyCycle

This command sets the chip in sniff mode so that it regularly looks for new packets. This is the listen mode.

When this command is sent in STDBY_RC mode, the context (device configuration) is saved and the chip enters in a loop defined by the

following steps:

• The chip enters RX and listens for a packet for a period of time defined by rxPeriod

• The chip looks for a preamble in either LoRa or FSK

• Upon preamble detection, the timeout is stopped and restarted with the value 2 * rxPeriod + sleepPeriod

• If no packet is received during the RX window (defined by rxPeriod), the chip goes into SLEEP mode with context saved for a period of

time defined by sleepPeriod

• At the end of the SLEEP window, the chip automatically restarts the process of restoring context and enters the RX mode, and so on. At

any time, the host can stop the procedure.

The loop is terminated if either:

• A packet is detected during the RX window, at which moment the chip interrupts the host via the RX_DONE flag and returns to

STBY_RC mode

• The host issues a SetStandby(...) command during the RX window (during SLEEP mode, the device is unable to receive

commands straight away and must first be waken up by a falling edge of NSS).

The SLEEP mode duration is defined by:

Sleep Duration = sleepPeriod * 15.625µs

The RX mode duration is defined by

Rx Duration = rxPeriod * 15.625µs

The following figure highlights operations being performed while in RxDutyCycle mode. It can be observed that the radio takes around 1ms

to save the context, go into SLEEP mode, re-initialize the radio, lock the PLL and go into RX. The delay is not accurate and may vary depending

on the time needed for the XTAL to start, the PLL to lock, etc.

Table 13-12: SetRxDutyCycle SPI Transaction

Byte

1-3

4-6

Data from host

Opcode = 0x94

rxPeriod(23:0)

sleepPeriod(23:0)

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