Trouble with linemask-DIO assigning on Port WriteVi

[xxy]

"I am using LabView 5.1 and a datacard AT-Mio-16E-10 with Windows NT. Why does the linemask number on Port WriteVi don´t change the same port line?(port is const., digital channel,too) If I measure at Dio 1 and the linemask is 1, it is not changing the Dio 1, when I change the pattern. But if the linemasknumber at 2 or 3 , the Dio 1 changes in the right way.
Thanks for any reply.

[Dr._Imad]

The line mask (in binary: bit set to 1 ) affects the corresponding line.
line masks 2 (0000 0010) or 3 (0000 0011) sets bit 1 to 1 affecting DIO 1

see the modified vi to set the line mask for a particular line number