12. Serial Device Communications
12.1 Onboard SPI Support
The MCU onboard the Si5396J-A- EVB communicates with the Si5396 device through a 4-wire SPI (Serial Peripheral Interface) link.
The MCU is the SPI master and the Si5396 device is the SPI slave. The Si5396 device can also support a 2-wire I
2
C serial interface,
although the Si5396 EVB does NOT support the I
2
C mode of operation. SPI mode was chosen for the EVB because of the relatively
higher speed transfers supported by SPI vs. I
2
C.
12.2 External I
2
C Support
I
2
C can be supported if driven from an external I
2
C controller. The serial interface signals between the MCU and Si5396 pass through
shunts loaded on header J17. These jumper shunts must be installed in J17 for normal EVB operation using SPI with CBPro. If testing
of I
2
C operation via external controller is desired, the shunts in J17 can be removed thereby isolating the on-board MCU from the
Si5396 device. The shunt at JP1 (I2C_SEL) must also be removed to select I
2
C as Si5396 interface type. An external I
2
C controller
connected to the Si5396 side of J17 can then communicate to the Si5396 device. (For more information on I
2
C signal protocol, please
refer to the Si5396 data sheet.)
The figure below illustrates the J17 header schematic. J17 even numbered pins (2, 4, 6, etc.) connect to the Si5396 device and the odd
numbered pins (1, 3, 5, etc.) connect to the MCU. Once the jumper shunts have been removed from J17 and JP1, I
2
C operation should
use J17 pin 4 (DUT_SDA_SDIO) as the I2C SDA and J17 pin 8 (DUT_SCLK) as the I
2
C SCLK. Please note the external I
2
C controller
will need to supply its own I
2
C signal pull-up resistors.
Figure 12.1. Serial Communications Header J17
UG336: Si5396 Evaluation Board User's Guide
Serial Device Communications
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