This instruction marks the beginning of a stage, and stages can only be entered in Program code blocks. Each Program code block can have up to 128 stages and there cannot be duplicates stages, within the same code block. This is a 'power-rail' instruction. This just means that even though it is displayed on the left hand side of the logic, it is actually entered in on the right-hand side of the logic and then collapses down to the Power rail. The first Stage instruction in a Program code block, regardless of the stage number, will automatically become the "Initial Stage", and this will be indicated, as the initial stage, because it will have a double border. Whenever a Program code block is first enabled to run, the Initial Stage will automatically be enabled and all of the other stages will be disabled. After the first scan of the Program code block the Initial Stage will operate like any other stage in the Program code block.