The O means it is referencing a physical channel on an output module. O:5/0 (don't confuse O for zero or vice versa) All I/O references use 'slot 0' in MicroLogix project. NOTE: When programming a MicroLogix PLC, slot numbers do not apply since all the I/O is built in to the controller. The 1 means it is channel 1 (the second input channel on that module). The 2 means the input module is in slot 2 of the rack (the third slot from the left). The I means it is referencing a physical channel on an input module. I:2/1 (don't confuse I for one or vice versa) The point is, it is a value that represents 16 items that can be 1 or 0.in other words 16 bits.Īn address that references the input of a SLC500 input module. A word sometimes is called an integer or a register. In RSLogix 500, the address of the bit can be shown a couple different ways. Bits can also be internal coils (internally used in a PLC program but not tied to any real inputs or outputs). Discrete inputs and outputs are examples of bits. BitsĪ bit is computer-speak for a value or register that can only be a 1 or a 0 true or false.

NOTE: This is an original post, however it was inspired by a similar post at. If you don't already have RSLogix 500 or Micro yet, you can get it along with RSLinx and RSLogix Emulate 500 by watching the first video in my FREE Mini PLC CourseĪlso, if you want an introduction to Ladder Logic before you start, check out this post. For everyone else, open up your RSLogix 500 (or 5 or Micro) and let's get to work. If you're new to Allen-Bradley PLC programming, I'm going to give you some information that you can put to work.immediately! In this free Allen-Bradley PLC training tutorial I'll walk you through the basics of addressing discrete inputs, outputs, binary bits, timers and counters.įor this basic PLC training tutorial, you will need RSLogix 500 or Micro to be able to test the concepts of this post.

Allen bradley ladder logic program