DS92LX1622: i2c NACK on far end

Hello,

We are having problems with i2c pass through mode of DS92LX162x. When want to access something on far end we get NACK back on the near end i2c bus. While we see ACK on far end i2c bus.

We have the following setup:



For FPGA we have tried different controllers: Xilinx axi iic, xilinx PS i2c and bitbanging. But all the same results.

We also tried lowering the speed from 100 KHz to 50 KHz. (and update DS92LX162x to reflect that speed)

We can talk to DS92LX1622 and setup the registers. But we cannot talk to anything on far end i2c bus.

We connected a scope to both i2c busses, and we see this:


blue: SDA near end
yellow: SCL near end
green: SDA far end
purple: SCL far end

As you can see the ACK is received on far end, but near end gives NACK.
pass through is set (register 0x3) is set for both near and far end. (default value)

We also don't see link crc errors.


As I understand from datasheet, we don't need to set ID[*] index/match in i2c pass through?

We simple don't understand why we get a NACK.

Can someone give me a reason why we get a NACK?

Thanks Marc