Is the high impedance mode of the data bus lines just controlled by the
RD-Signal or also by the CS-Signal?
What is the max. current load of data bus signals?
The output buffer is enabled when CS and RD are held low, both RD-Signal and
CS-Signal are needed for high impedance control.
The datasheet specifies 2mA/-1mA load conditions for data bus electrical
specifications (page 5 of datasheet).