the program is as follows:

org 0000h
mov dptr,#0F003H
mov a,#10000000B
movx @dptr,a
mov dptr,#0F000H
mov a,#0AAH
movx @dptr,a
end

the 8255 is mapped to address F000-F003 and i connected the A15,A14,A13,A12 address pins of the 8051 to NAND gate and the output of the NAAND gate is connected to the 8255 CS*

regards
george