SI4X55-C Datasheet, PDF (22/39 Pages) Silicon Laboratories – Preamble sense mode

Si4x55-C
5. Controller Interface
5.1. Serial Peripheral Interface
The Si4x55 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 listed in Table 11. The host MCU writes data over the SDI pin and can read data from the device on the SDO
output pin. Figure 10 shows 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 API 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.
Table 11. Serial Interface Timing Parameters
Symbol
Parameter
Min
(ns)
t_CH
Clock high time
40
t_CL
Clock low time
40
t_DS
Data setup time
20
t_DH
Data hold time
20
t_DD Output data delay time
t_DE
Output disable time
t_SS
Select setup time
20
t_SH
Select hold time
50
t_SW
Select high period
80
Max
(ns)
43
45
SCLK
tSS
SDI
SDO
nSEL
Diagram
tCL
tCH
tDS tDH
tDD
*Note: CL = 10 pF; VDD = 1.8 V; SDO Drive strength setting = 10.
tSH tDE
tSW
nSEL
SDO
SDI
SCLK
API Command
ParamByte 0
Figure 10. SPI Write Command
ParamByte n
22
Rev 1.0