Don't Use the instruction mov a,p0 or mov p0,a,because as you are using a latch 74HC373, the p0 and p1 internal SFRs are used. you can address the DAC,like use some decoder, generate a chip select,then use the p0 as accumulator

ex: if suppose i am using a 2 to 4 decoder say 74ls/hct139. connect input of decoder A0 and A1 and rest not connected. use Y0 or Y3 and connect to DAC's chip select.Then

write instruction as mov r0,#00
mov a,@r0
this will fetch you the required data