i have a dac max517 in my application which won't run :

Code:
schematic:

            |--V--|
v-meter ----|     |---- Vdd (Ref0)     
gnd     ----|     |---- Vdd
scl     ----|     |---- gnd (AD0)
sda     ----|     |---- gnd (AD1)
            |-----| 

code:

slad con %01011000 ' slave address 00
comb con %00000000 ' command byte

volt var byte ' output voltage

init : clear

high sda
high scl

volt = 255

SHIFTOUT sda, scl, 5, [slad, %0\1, comb,  %0\1, volt,  %0\1]
as result : the v-meter output stays ever 0V. can't see what i make wrong. thanks for any help