Let's consider an interface between a simple microprocessor and a certain memory. For instance, let's assume that the microprocessor drives the address bus, a read signal, a write signal, and that the data bus is a bidirectional signal, which can be driven by the processor or by the memory depending on if it is doing a reading or a writing.
In that case, it is necessary that after a reading, the memory puts its output on data bus at high impedance, and that after a writing, the processor puts its output on data bus at high impedance. Both operations to avoid conflicts.
But what if for instance we have a data bus for reading (driven by the memory) and a data bus for writing (driven by the processor)? Is it necessary (or anyway better) that the processor puts its output on the databus he drives at high impedance after a writing operation?