SI4455 Datasheet, PDF (22/40 Pages) Silicon Laboratories – 20-Pin 3x3 mm QFN package

Si4455
5. Controller Interface
5.1. Serial Peripheral Interface
The Si4455 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 8 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
SCLK
t_DS
Data setup time
20
tSS
t_DH
Data hold time
20
t_DD Output data delay time 20
S_SD_DI_N
t_EN
Output enable time
20
t_DE
Output disable time
t_SS
Select setup time
50
SDO
20
t_EN
t_SH
Select hold time
50
nSEL
t_SW
Select high period
80
Diagram
tCL
tCH
tDS tDH
tDD
tSH
tDE
t_SW
nSEL
SDO
SDI
SCLK
API Command
ParamByte 0
Figure 8. SPI Write Command
ParamByte n
22
Rev 1.1