I'm using the ATtiny1614's UART with a half-duplex RS-485 driver to connect multiple devices on a shared bus. To avoid data collisions, I'd like to determine whether the UART is currently receiving data before starting to send data myself. This is only a best-effort solution, nothing like the robustness of CAN. But if the device can see data currently coming in, it shouldn't start shouting against that (enabling the driver), knowing better that this won't help anybody.
I've found the start frame detection feature, but it's documented to work only in standby/sleep modes, not when active.
Is there another way to find out whether the UART currently receives data, before the reception is complete and the Receive Complete interrupt (RXCIF) is set?