The reverse channel in GMSL1 SerDes parts is used both for data (I2C or UART) and control signal (GPI/GPO or Interrupt - INT). The transmission of a control signal transition (1->0 or 0->1) takes about 300us, and the time taken to send data depends on the data rate.
Many GMSL1 parts allow data and control signal transmissions to overwrite each other, so it is necessary to prevent this at the system level, by making sure that a control signal does not change while data is being sent, and that data is not sent for at least 400us after change of a control signal.
This restriction completely applies to earlier GMSL1 devices: MAX9249, MAX9259, MAX9260, MAX9263, MAX9264, MAX9265, MAX9266 and MAX9268.
In newer GMSL devices: MAX9240, MAX9271, MAX9272, MAX9273, MAX9275, MAX9276, MAX9277, MAX9278, MAX9279, MAX9280, MAX9281, MAX9282, MAX9288, MAX9290, MAX9291, and MAX9293, control signal transmission will always succeed although it may overwrite data.
In the latest GMSL1 parts: MAX9286, MAX96705, MAX96706, MAX96707, MAX96708, MAX96709 and MAX96711, there are no restrictions. If the control signal changes during an I2C transaction, it is delayed until the I2C can be stopped by not sending an acknowledge. If an I2C transaction starts during transmission of INT, acknowledge for the I2C will be delayed until the INT sequence has completed.