When initializing the communications link between the DS90UB662-Q1 deserializer hub and a DS90UB633A-Q1 serializer, the system timing will depend on the mode selected for generating the serializer reference clock. When synchronous clocking mode is selected, the serializer will re-lock onto the extracted back channel reference clock once available, so there is no need for local crystal oscillator at the sensor module (Figure 9-2). When the DS90UB633A-Q1 is operating in non-synchronous mode, or is connecting to DS90UB633A-Q1 serializer, the sensor module requires a local reference clock and the timing would follow Figure 9-3.

Figure 9-2 Power-Up Sequencing With Synchronous Clocking Mode

Figure 9-3 Power-Up Sequencing With Non-Synchronous Clocking Mode