I decided to use two 74LVCH8T245 on a board: one is used two translate a bidirectional bus from +5V to +3.3V, the other one is used as a simple bus buffer with the same Vcca and Vccb (+3.3V).
I started to test the one with the same power supply for A and B ports. I connected DIR and OE to Vcca=Vccb=+3.3V. In this condition, all the A and B ports are in tristate. 100k pull-ups are connected on A port signals. B signals are left floating.
When I put the voltmeter probe on A signal, I read a low-voltage (about 0.1V), but it has a pull-up and the pin should be in tristate! What could happen? I replaced the chip three times and the behaviour is always the same. If the probe is touching the A signal during power-up, I can read a high voltage (correct), but as soon as I disconnect the probe and connect it again, I start reading low voltage!
Another question. The bus is bidirectional, so there will be some (maybe short) intervals where all the devices on the bus are tristated. Is it important to connect small pull-up or pull-down (100k) on each bus signal?
