DS92LX1621 Datasheet, PDF (33/44 Pages) National Semiconductor (TI) – 10 - 50 MHz Channel Link III Serializer and Deserializer with Embedded Bi-Directional Control Channel

I²C PASS THROUGH
I²C pass-through provides an alternative means to indepen-
dently address slave devices. The mode enables or disables
I²C bidirectional control channel communication to the remote
I²C bus. This option is used to determine whether or not an
I²C instruction is to be transferred over to the remote I²C de-
vice. When enabled, the I²C bus traffic will continue to pass
through and will be received by I²C devices downstream. If
disabled, I²C commands will be blocked to the remote I²C
device. The pass through function also provides access and
communication to only specific devices on the remote bus.
The feature is effective for both Camera mode and Display
mode.
For example in the configuration shown in Figure 27:
If master controller transmits I²C transaction for address
0xA0, the SER A with I²C pass through enabled will transfer
I²C commands to remote Camera A. The SER B with I²C pass
through disabled, any I²C commands will be bypassed on the
I²C bus to Camera B.
FIGURE 27. I²C Pass Through
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SYNCHRONIZING MULTIPLE CAMERAS
For applications requiring multiple cameras for frame-syn-
chronization, it is recommended to utilize the General Pur-
pose Input/Output (GPIO) pins to transmit control signals to
synchronize multiple cameras together. To synchronize the
cameras properly, the system controller needs to provide a
field sync output (such as a vertical or frame sync signal) and
the cameras must be set to accept an auxiliary sync input.
The vertical synchronize signal corresponds to the start and
end of a frame and the start and end of a field. Note this form
of synchronization timing relationship has a non-deterministic
latency. After the control data is reconstructed from the bi-
directional control channel, there will be a time variation of the
GPIO signals arriving at the different target devices (between
the parallel links). The maximum latency delta (t1) of the GPIO
data transmitted across multiple links is 25 μs.
Note: The user must verify that the timing variations between
the different links are within their system and timing specifi-
cations.
For example in the configuration shown in Figure 28:
The maximum time (t1) between the rising edge of GPIO (i.e.
sync signal) arriving at Camera A and Camera B is 25 μs.
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