Steve:
It depends on the type of port pins involved. The best order of business when powering down the display is to set all pins to low levels before the power down and then keeping them there. On some systems it may be necessary to buffer the lines through some type of CMOS buffer.

Not all instances when I have used this technique has the I/O pins been owned by an 8052 type part. In the case of a recent 'GP32 project I just set all the pins to Input state on the processor (GP32 pins as inputs with the programmable pullups turned off are very high impedance and do not cause latchup to the display controller.

Michael Karas