The standard signal definitions of RS232 use those names (RxD, TxD) so it is clear what they mean on the RS232 end. However, when one has to name the signals at the MCU, and at the level shifter, which ones are D and Q can become a point of confusion. Nonetheless, it would be wise to define them in some rigorous way, so the risk of confusion is minimized. At the MCU, I presently prefer to call the level shifter's driven signal, an OUTPUT from the MCU, TxQ and the driving signal, an INPUT to the MCU, RxD. That way, TxQ ends up as TxD at the RS232 cable, and RxD ends up as RxD. Now, there can still be confusion as to which end of the cable that might be ...

It's long been a convention to call a combinatorial input A and a combinatorial output Y. It's been a convention for just as long to call the output of a clocked element Q. Since the output from the MCU is clocked, and since the input to the MCU is not, at least locally, that's consistent with the above. Since the signals into and out of the level shifter are combinatorial, perhaps that will apply as well.

Since netlisters don't like different signal names attached to the same node, I don't know what will work best for singal naming between the level shifter and the connector.

You can't have too much clarity.

RE