Direct Variable I/O Memory - LS Electric XGB PLC from AutomationDirect

To view the real-world I/O for this PLC, we are going to look at the “I/O Parameter” screen. To get there, we will go to the project browser on the left side of the screen and double click on “I/O Parameter.” A new window opens with the I/O Parameter screen and a graphic of our PLC. If we mouse over the different input and output points, we will see direct variable addresses allocated for those points. Digital input points are squares and are in the %I range of memory addresses. Digital output points are circles and are in the %Q range of memory addresses. Note that the digital direct variables are organized by slot. The PLC doesn’t grab the next available register, it utilizes the range associated with the slot number. Using a digital input card in slot 3 for instance, will utilize the %IX0.3.X range of addresses, even if the %IX0.1.X and 0.2.X ranges are unused. For analog and specialty modules, the PLC uses %U memory addresses. These are not viewable in the I/O Parameter section, but when you add an analog or specialty module to your PLC design, the software requires creation of global variables. These Global variables can be custom named in the variable column and they are automatically mapped to the correct direct variable address and of the correct data type. Note that analog Boolean values like status bits will be at %UX locations and analog word values like raw counts will be at %UW locations.