As can be seen from the waveform in the manual, RX ignores the first transition starting with high impedance (or 0), resulting in RX missing a transition and RZI decoding error.
I'd like to ask about NXP TJA1410. In this case, are there any recommended decoding methods?
Hello @li_wang ,
First, could you please clarify whether this is a theoretical concern based on Figure 11 or whether you are observing an actual RZI decoding error in your implementation?
If an actual error is observed, please provide:
- TX, RX, ED and differential line voltage waveforms covering the TRANSMIT command and the beginning of data transmission
- The digital PHY or custom decoding implementation connected to the TJA1410
- The point at which the implementation starts treating RX as valid
- The expected and actually decoded data sequence
Regarding Figure 11, the highlighted VLINE transition occurs during the transition from Normal mode to Transmitting mode. At this time, the line impedance changes from High-Z to active impedance and the transmitter begins driving the differential line. The RX output is explicitly marked as undefined during this transition. Therefore, the initial VLINE movement shown in the highlighted area should not be interpreted as a valid RZI data transition that must be represented by a pulse on RX.
In Normal and Transmitting modes, the default level on RX is HIGH. When the differential MDI voltage crosses the receiver trigger threshold, the TJA1410 generates a LOW pulse on RX. This behavior applies to the valid receive-data interval.
Consequently, Figure 11 does not indicate that the TJA1410 ignores the first valid RZI transition. It shows that RX is not defined during transmitter activation. Valid RZI decoding should begin only when RX is in its valid operating interval, not from the initial analog VLINE movement caused by the mode transition.
Best regards,
Pavel