Si4430/31/32-B1
18
Rev 1.1
3. Controller Interface
3.1. Serial Peripheral Interface (SPI)
The Si4430/31/32 communicates with the host MCU over a standard 3-wire SPI interface: SCLK, SDI, and nSEL.
The host MCU can read data from the device on the SDO output pin. A SPI transaction is a 16-bit sequence which
consists of a Read-Write (R
/W) select bit, followed by a 7-bit address field (ADDR), and an 8-bit data field (DATA)
as demonstrated in Figure 3. The 7-bit address field is used to select one of the 128, 8-bit control registers. The
R
/W select bit determines whether the SPI transaction is a read or write transaction. If R
/W = 1 it signifies a WRITE
transaction, while R
/W = 0 signifies a READ transaction. The contents (ADDR or DATA) are latched into the
Si4430/31/32 every eight clock cycles. The timing parameters for the SPI interface are shown in Table 10. The
SCLK rate is flexible with a maximum rate of 10 MHz.
Figure 3. SPI Timing
To read back data from the Si4430/31/32, the R/W bit must be set to 0 followed by the 7-bit address of the register
from which to read. The 8 bit DATA field following the 7-bit ADDR field is ignored on the SDI pin when R/W = 0. The
next eight negative edge transitions of the SCLK signal will clock out the contents of the selected register. The data
read from the selected register will be available on the SDO output pin. The READ function is shown in Figure 4.
After the READ function is completed the SDO pin will remain at either a logic 1 or logic 0 state depending on the
last data bit clocked out (D0). When nSEL goes high the SDO output pin will be pulled high by internal pullup.
Table 10. Serial Interface Timing Parameters
Symbol
Parameter
Min (nsec)
Diagram
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
20
t
EN
Output enable time
20
t
DE
Output disable time
50
t
SS
Select setup time
20
t
SH
Select hold time
50
t
SW
Select high period
80
nSEL
SCLK
SDI
MSB
LSB
A2  A1  A0  D7  D6  D5  D4  D3  D2  D1 D0
A4
xx   xx
A3
RW  A7
A6 A5
RW
Data
Address
SDI
SCLK
DO
nSEL
t
CL
t
CH
DS
t
DH
t
DD
t
SS
t
E
t
SH
DE
SW