DS92LX1621_16 Datasheet, PDF (30/49 Pages) Texas Instruments – 10 - 50 MHz DC-Balanced Channel Link III Serializer and Deserializer with Bi-Directional Control Channel

DS92LX1621, DS92LX1622
SNLS327I – MAY 2010 – REVISED JANUARY 2014
www.ti.com
I²C PASS THROUGH
I²C pass-through provides an alternative means to independently 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 device. 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 31:
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.
DS92LX1621
DS92LX1622
CMOS
Image
Sensor
DIN[15:0]
PCLK
ROUT[15:0]
PCLK
SDA
SCL
I²C
Camera A
Slave ID: (0xA0) ^{SER A: I2C _MASTER}
I2C_PASS_THRU Enabled
DS92LX1621
CMOS
Image
Sensor
DIN[15:0]
PCLK
I²C
SDA
SCL
DES A: I2C_SLAVE
DS92LX1622
ROUT[15:0]
PCLK
ECU
Module
SDA
SCL
I²C
Camera B
Slave ID: (0xA0)
SER B: I2C_MASTER
I2C_PASS_THRU Disabled
I²C
SDA
SCL
DES B: I2C_SLAVE
Figure 31. I²C Pass Through
2C
Master
SYNCHRONIZING MULTIPLE CAMERAS
For applications requiring multiple cameras for frame-synchronization, it is recommended to utilize the General
Purpose 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
specifications.
For example in the configuration shown in Figure 32:
The maximum time (t1) between the rising edge of GPIO (i.e. sync signal) arriving at Camera A and Camera B is
25 μs.
30
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