hi,

{ 
1 LCD_RD = 1; 
2 LCD_CD = 0; 
//3 P0 = dados; 
4 LCD_CE = 0; 
5 LCD_WR = 0; 
6 LCD_WR = 0; 
7 LCD_WR = 1; 
8 LCD_CE = 1; 
//9 P0 = 0xFF; 
}

Looking on this code I see that steps 5 and 6 duplicate each other. Assume, it is not a mistake but for timing conditions. If so then we may calculate that /WR pulse should be at least 24 oscillator periods.
Now, as we know, external data memory access may be done with MOVX instruction. With standard AT89C51 you use, /WR and /RD pulses of MOVX instruction take 6 clock cycles. Unfortunatelly their duration may not be increased with standard derivative. So I think it is not possible for you to work with LCD as memory mapped device.

Regards,
Oleg