Why did SNUM get warning in functional block?

[ridgemao]

I got warning with "SNUM" command used in functional block: WARNING: SNUM(638): Operand data size is unknown. Check the control data value and the size of arrays or variables of other operands. Rung 3 (6,0). I had defined a stack using "SSET" command in this functional block without any warnings. And if I assigned the functional block's AT property for the TB operand of "SNUM", no warnings any more. Is this a bug for CX-Programmer v9.12? Or is there any other method for me to get the size of the stack defined by SSET? The attachment is the screenshot of my program's warning. Edited January 12, 2011 by ridgemao