Following is my as given on microchip website
GET_AD:
SETB CS ; set cs hi
MOV COUNTA,#15 ;
NXTBIT:
CLR DCLK ; X,X,NULL,D11,D10,D9...D0
CLR CS ; CS low to start conversion or keep low
SETB DCLK ; raise the clock
MOV C,SDAT ; put data into C flag
RLC A ; shift C into Acc (A/D low bits)
XCH A,ADRESH ; get ADRESH byte
RLC A ; shift C into Acc (A.D high bits)
XCH A,ADRESH ; get low bits back into Acc for
DJNZ COUNTA,NXTBIT
MOV ADRESL,A ; put A into ADRESL
ANL ADRESH,#0FH ; mask off unwanted bits (x,X,X,Null)
SETB CS ; set CS hi to end conversion
RET