No Ground PIN Available at D-Sub Connector of Vector BroadR-Reach (BR) Interfaces

There is a big difference concerning the galvanic isolation of CAN interfaces and DC isolation of BroadR-Reach interfaces.

According to the Open Alliance TC1 100BASE-T system implementation specification in Chapter 7.2 Interface circuitry definition, a BR-Bus shall be DC isolated at the analog front end (i. e. between BR-Phy and D-Sub). Therefore there is no DC reference of the BR-Bus. Whereas a CAN bus is isolated on the digital side of the transceiver (i. e. before the transceiver) and the CAN-Signal refers to GND of the transceiver.

This is the reason why, the Vector interfaces for BR have no ground connected to the D-Sub. The Vector interfaces for CAN bus have the supply ground of the transceiver connected to D-Sub pin 3.

Consequently, no ground shift test is sensible for BroadR-Reach. Moreover, shifting any ground to the D-Sub shield of Vector interface might have fatal consequences for the interface and the PC it is connected to. Because D-Sub shield is identical with system GND and USB GND.