The 8CS line is the active-low chip select line for the 8279 IC on the display board, and disregarding shadow copies, should correspond to 0x2008-0x200B.
A00 is the mode select line for the 8279; when address 0x2008 is selected, this line should be low, putting the 8279 in data mode. When 0x2009 is selected, this line should be high, putting the 8279 in command mode.