SI4463 datasheet(16/53 Pages) SILABS

16 / 53 page

Si4463/61/60-C

Rev 1.0

3. Controller Interface

3.1. Serial Peripheral Interface (SPI)

The Si446x communicates with the host MCU over a standard 4-wire serial peripheral interface (SPI): SCLK, SDI,

SDO, and nSEL. The SPI interface is designed to operate at a maximum of 10 MHz. The SPI timing parameters

are demonstrated in Table 9. The host MCU writes data over the SDI pin and can read data from the device on the

SDO output pin. Figure 3 demonstrates an SPI write command. The nSEL pin should go low to initiate the SPI

command. The first byte of SDI data will be one of the firmware commands followed by n bytes of parameter data

which will be variable depending on the specific command. The rising edges of SCLK should be aligned with the

center of the SDI data.

Figure 3. SPI Write Command

The Si446x contains an internal MCU which controls all the internal functions of the radio. For SPI read commands

a typical MCU flow of checking clear-to-send (CTS) is used to make sure the internal MCU has executed the

command and prepared the data to be output over the SDO pin. Figure 4 demonstrates the general flow of an SPI

read command. Once the CTS value reads FFh then the read data is ready to be clocked out to the host MCU. The

typical time for a valid FFh CTS reading is 20 µs. Figure 5 demonstrates the remaining read cycle after CTS is set

to FFh. The internal MCU will clock out the SDO data on the negative edge so the host MCU should process the

SDO data on the rising edge of SCLK.

Table 9. Serial Interface Timing Parameters

Symbol

Parameter

Min

(ns)

Max

(ns)

Diagram

tCH

Clock high time

tCL

Clock low time

tDS

Data setup time

tDH

Data hold time

tDD

Output data delay time

tDE

Output disable time

tSS

Select setup time

tSH

Select hold time

tSW

Select high period

*Note:

CL = 10 pF; VDD = 1.8 V; SDO Drive strength setting = 10.

SCLK

SDI

SDO

nSEL

tCL

tSS

tCH

tDS

tDH

tDD

tSH tDE

tSW

FW Command

Param Byte 0

Param Byte n

nSEL

SDO

SDI

SCLK

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