LLCC68 datasheet(50/111 Pages) SEMTECH

50 / 111 page

LLCC68

Data Sheet

Rev. 1.1

DS.LLCC68.W.APP

Dec 2024

50 of 111

Semtech

LLCC68

www.semtech.com

8.3 Multi-Purpose Digital Input/Output (DIO)

The chip is interfaced through the 4 control lines which are composed of the BUSY pin and 3 DIOs pins that can be configured as interrupt,

debug or to control the radio immediate peripherals (TCXO or RF Switch).

8.3.1 BUSY Control Line

The BUSY control line is used to indicate the status of the internal state machine. When the BUSY line is held low, it indicates that the internal

state machine is in idle mode and that the radio is ready to accept a command from the host controller.

The BUSY control line is set back to zero once the chip has reached a stable mode and it is ready for a new command. Inherently, the amount

of time the BUSY line stays high depends on the nature of the command. For example, setting the device into TX mode from the STDBY_RC

mode takes much more time than simply changing some radio parameters because the internal state machine maintains the BUSY line high

until the radio is effectively transmitting the packet.

Figure 8-3: Switching Time Definition

For the internal state machine, all “write” commands cause the BUSY line to be asserted high after time TSW,as per the graph above. TSW

represents the time required for the internal state machine to wake-up and start processing the command.

Conversely, the “read” command is handled directly without the help of the internal state machine and thus the BUSY line remains low after

a “read” command.

The max value for TSW from NSS rising edge to the BUSY rising edge is, in all cases, 600ns.

In Sleep mode, the BUSY pin is held high through a 20kΩ resistor. The BUSY line goes low as soon as the radio leaves Sleep mode.

In FS, BUSY goes low when the PLL is locked.

In RX, BUSY goes low as soon as the RX is up and ready to receive data.

In TX, BUSY goes low when the PA has ramped-up and transmission of preamble starts.

In addition to this, the BUSY also goes high to handle its internal IRQ. In this scenario, it is essential to wait for the BUSY line to go low before

sending an SPI command (either a “read” or “write” command).

Figure 8-4: Switching Time Definition in Active Mode

BUSY

NSS

SPI

(MOSI, MISO, SCK)

opcode

Param1

Param…

BUSY

NSS

SPI

(MOSI, MISO, SCK)

opcode

Param1

Param…

Mode

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