MWD,
There are a number of System Operands in the vision series that are very helpful in programming. Here are two ways to view.
In Visilogic ladder, bottom half of display, bottom tabs, select Operands. In the left hand window there are SB's, SI's, and SL's. Selecting one of these populates the right hand window with the basic descriptions as well as the present values if you are on line with the plc.
In Visilogic ladder, select help, search, System Operands, and you will find much more detailed descriptions of the functions of these operands. It is best to use these as read only for the most part although there are a few that can be manipulated in a positive way.
Regards,
Sparky