A bit off thread here bit still relavant
I have used dual port memory to interface 8051 to other systems. On Intel devices, and probably others, the interrupt line is checked a clock cycle after the address is put out. If the address conflict output of the dualport memory is connected to the 8051 interruput when an address conflict occurs an interrupt routine is entered at the instruction folowing the MOVX to dual port memory. the code would read

dual_port_coflict_int:
setb dp_conflict
reti

read_dual_port:
mov dptr,#dual_port_ram
dp_rd:
movx a,@dptr
jbc dp_conflict,dp_rd
ret

In order to interface to PCMCIA you may need to use a PLD to operate the PCMCIA interface to dual port ram