Datasheet

20 SERDESUB-16USB User’s Guide SNLU100 – April 2012
Evaluation of the Bi-directional Control Channel
This section describes how to perform I
2
C instructions between MCU/FPGA and a remote
peripheral device through the DS90UB902Q and DS90UB901Q pair configured in a
camera type of application. Figure 4 shows the configuration of evaluation boards for I
2
C
communication. A MCU/FPGA controller with an I
2
C interface is required. Refer to the
DS90UB901Q/902Q datasheet for the definition of each register.
SCL
SDA
VDD18
VDDIO
VDD18
VDDIO
Figure 4. Example of DS90UB901Q/902Q in Camera Application
Camera Mode:
In Camera mode, I
2
C transactions originate from the Master controller at the Deserializer
side (Figure 4). The I
2
C slave core in the Deserializer will detect if a transaction is
intended for the Serializer or a slave at the Serializer. Commands are sent over the bi-
directional control channel to initiate the transactions. The Serializer will receive the
command and generate an I
2
C transaction on its local I
2
C bus. At the same time, the
Serializer will capture the response on the I
2
C bus and return the response on the forward
channel link. The Deserializer parses the response and passes the appropriate response
to the Deserializer I
2
C bus.