CC2420-RTR1 datasheet(32/92 Pages) TI

32 / 92 page

CC2420

SWRS041B

Page 32 of 89

CSn

ADDR

DATA

8MSB

DATA

8LSB

DATA

ADDR+1

ADDR

TXFIFO

DATA

ADDR

DATA

ADDR+2

Status

Command

Strobe

Read

TXFIFO

Write

Figure 11. Multiple SPI Access Example

14 Microcontroller Interface and Pin Description

When used in a typical system,

CC2420 will

interface

microcontroller.

This

microcontroller must be able to:

• Program

CC2420 into different modes,

read and write buffered data, and read

back status information via the 4-wire

SPI-bus configuration interface (SI, SO,

SCLK

and CSn).

• Interface to the receive and transmit

FIFOs using the FIFO and FIFOP

status pins.

• Interface to the CCA pin for clear

channel assessment.

• Interface to the SFD pin for timing

information (particularly for beaconing

networks).

14.1

Configuration interface

CC2420 to microcontroller interface

example is shown in Figure 12. The

microcontroller uses 4 I/O pins for the SPI

configuration interface (SI, SO, SCLK and

CSn

). SO should be connected to an input

at the microcontroller. SI, SCLK and CSn

must

microcontroller

outputs.

Preferably the microcontroller should have

a hardware SPI interface.

The microcontroller pins connected to SI,

and SCLK can be shared with other

SPI-interface devices. SO is a high

impedance output as long as CSn is not

activated (active low).

CSn

should have an external pull-up

resistor or be set to a high level when the

voltage regulator is turned off in order to

prevent the input from floating. SI and

SCLK

should be set to a defined level to

prevent the inputs from floating.

CC2420

µC

CSn

SCLK

MOSI

MISO

SCLK

GIO2

FIFO

FIFOP

CCA

SFD

GIO0

Interrupt

GIO1

Timer Capture

Figure 12. Microcontroller interface example

CC2420-RTR1 Datasheet(PDF) 32 Page - Texas Instruments

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