SAE J1708 is basically an RS485 hardware interface without the typical 120 ohm termination resistors. In typical applications, a half-duplex RS485 transceiver chip is used to connect to the bus.
In order to avoid collisions, J1708 protocol rules dictate that the device must monitor the data bus while transmitting the first byte (MID) of its message.
How is this possible using a half-duplex transceiver? In other devices I have worked with, half-duplex implied that receiving during transmission was not possible. Does the Receiver Output pin of the transceiver match the Driver Input during transmission?