Try this;
Code:
X VAR WORD
Y VAR WORD

AD_10BIT:
    FOR X = 0 TO 1023  ' Simulate 0 TO 5V
    Y = X */ 1251      ' For 10-bit A/D (5V/1023)*256 = 1.251
    SEROUT GPIO.1,N2400, ["X = ",DEC X," : = ",DEC Y DIG 3,".",DEC3 Y,"V",13,10]
    NEXT