Single TXB0104 or double TXB0104s for SPI communication?

I'm new to TXB0104. I read through the datasheet but I have a question regarding the operation of TXB0104. The TXB0104 does voltage translation between two ports A and B. But I was wondering if a Channel on Port A can be input while another channel on the Port A is Output.

For example, I am designing an application where two uControllers are required to communicate with each other using SPI. However one uController runs at 3.3V while the other is running at 5V. Since SPI requires data to move in both directions, i was wondering if a single TXB0104 can be used for SPI level translation between two uControllers.

Or do I have to use two TXB0104s, one for either direction of data-flow?

Joe!