LLCC68 datasheet(47/106 Pages) SEMTECH

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LLCC68

Data Sheet

Rev. 1.0

DS.LLCC68.W.APP

July 2019

47 of 106

Semtech

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 will stay high depends on the nature of the command. For example, setting

the device into TX mode from the STDBY_RC mode will take much more time than simply changing some radio parameters

because the internal state machine will maintain 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 will 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 will be handled directly without the help of the internal state machine and thus the BUSY

line will remains low after a “read” command.

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

In Sleep mode, the BUSY pin is held high through a 20 kΩ resistor and the BUSY line will go low as soon as the radio leaves

the Sleep mode.

In FS, BUSY will go low when the PLL is locked.

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

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

BUSY

NSS

SPI

(MOSI, MISO, SCK)

opcode

Param1

Param…

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