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8.2 SPI Interface
When in SPI mode, the serial interface operates in 4-wire or 3-wire depending on the state of the SPI_3WIRE configuration bit. The
4-wire interface consists of a clock input (SCLK), a chip select input (CS), serial data input (SDI), and serial data output (SDO).
The 3-wire interface combines the SDI and SDO signals into a single bidirectional data pin (SDIO). Both 4-wire and 3-wire interface
connections are shown in the following figure.
To SPI Host
SDI
SDO
Si5340/41
I2C_SEL
SCLK
CS
SPI_3WIRE = 0
SPI 4-Wire
CS
SDIO
I2C_SEL
SCLK
SPI_3WIRE = 1
SPI 3-Wire
To SPI Host
To SPI Host
Si5340/41
Figure 8.6. SPI Interface Connections
Table 8.2. SPI Command Format
Instruction
I
st
Byte
2
nd
Byte
3
rd
Byte
n
th
Set Address
000x xxxx
8-bit Address
—
—
Write Data
010x xxxx
8-bit Data
—
—
Read Data
100x xxxx
8-bit Data
—
—
Write Data + Address Increment
011x xxxx
8-bit Data
—
—
Read Data + Address Increment
101x xxxx
8-bit Data
—
—
Burst Write Data
1110 0000
8-bit Address
8-bit Data
8-bit Data
1. X = don’t care (1 or 0)
2. The Burst Write Command is terminated by de-asserting CSb (CSb = high)
3. There is no limit to the number of data bytes that may follow the Burst Write command, but the address will wrap around to 0 in
the byte after address 255 is written.
Writing or reading data consist of sending a “Set Address” command followed by a “Write Data” or “Read Data” command. The 'Write
Data + Address Increment' or “Read Data + Address Increment” commands are available for cases where multiple byte operations in
sequential address locations is necessary. The “Burst Write Data” instruction provides a compact command format for writing data since
it uses a single instruction to define starting address and subsequent data bytes. The following figure shows an example of writing three
bytes of data using the write commands. This demonstrates that the “Write Burst Data” command is the most efficient method for writing
data to sequential address locations.
Si5341, Si5340 Rev D Family Reference Manual • Serial Interface
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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Rev. 1.3 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 26, 2021
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