function add48, op1, op2

result = bytarr(8)

temp1 = 0l
temp2 = 0l
temp3 = 0l
mask = ['000000ff'x, '0000ff00'x, '00ff0000'x, 'ff000000'x]

for i = 0, 3 do begin
    temp1 = ishft ((op1 and mask(i)), - i*8)
    temp2 = ishft ((op2 and mask(i)), - i*8)
    temp3 = temp1 + temp2 + temp3
    result(i) = ishft ((temp3 and 'ff'x), i*8)
    temp3 = ishft (temp3, -8)
endfor