DN stands for “done”.įor example, if counter C5:0 is a CTU (counter up), then the bit C5:0/DN will turn on after the counter has reached its preset value. You can address this bit by simply putting a “/DN” after the counter address. Each counter has bits that turn on after the counting function is complete. The address C5:0 simply refers to the counter. There are different types of counters available in the RSLogix, but the CTU (counter up) instruction covers everything we will talk about here.Ĭounters in A-B SLC and MicroLogix processors use file 5.Ĭ5:0 means that it references an internal Counter fileĬ5: 0 means that it uses the first counter in the table DN stands for “done”.įor example, if timer T4:0 is a TON (timer on delay), then the bit T4:0/DN will turn on after the timer has reached its preset value.Ī counter is a programmable instruction that lets you turn on or turn off bits after a preset count has been reached. You can address this bit by simply putting a “/DN” after the timer address. Each timer has bits that turn on after the timing function is complete. The address T4:0 simply refers to the timer. T4: 0 means that it uses the first timer in the table T4:0 means that it references an internal Timer file Timers in A-B SLC and MicroLogix processors use file 4 for their timers. The two primary types of timers are TON for “timer on delay” and TOF for “timer off delay”. In this case, the default file number is 3.Ī timer is a programmable instruction that lets you turn on or turn off bits after a preset time. Note that, unlike the Output and Input files, you have to use the file number in the address. There are many other words in other files that have bits you can use as internal coils, but we are going to stick with the B3 file for our application.ī3:0/0 means that it references an internal Binary fileī3: 0/0 means that it uses the first word in the tableī3:0/ 0 means that it is the first bit in the word. In RSLogix, the “B3” (binary) file is commonly used for all the internal coils. The “contacts” of this “relay” can then be used multiple times in other parts of the program. Internal coils are used to store information. The internal coil has no connection to the outside world. This is a programmable bit used to simulate a relay within the PLC. HARDWIRED OUTPUT – a physical connection from the PLC to an output device (relay or pilot light, etc.) As was said above, an address that references an output of an SLC 500 is O:5/0. I:4/ 0 means that it is the first input on the card.ĭon’t get the capital “I’s” confused with ones. I: 4/0 means that it uses Slot 4 (the 5th slot in the rack). An address that describes an input on an SLC 500 is I:4/0. HARDWIRED INPUT – a physical connection to the PLC from an input device (switch or sensor, etc.).Īllen-Bradley uses the capital letter “I” to designate a hardwired input.
The first rung in a ladder program is always 0000. Just like in an electrical ladder diagram, a rung has some type of output that is turned on or turned off by the preceding entities in the rung. RUNG – A section of the PLC ladder program that terminates in an output function of some type. O:0/ 5 means that it is the fifth output on the PLC.īy the way, don’t get the capital “O” confused with a zero.
O: 0/5 means that it uses Slot 0 (in the case of the 1100, this output is onboard) O:0/5 means that it is a physical output. The default is:įor example, an address that references an output of a MicroLogix 1100 is O:0/0. In RSLogix, there are a couple of ways to show the address of a bit. It can be an input, output or internal coil, among others. A few of the most common instructions are described below.īIT – an address within the PLC. An XIC (it looks like a normally open contact –] [– ) is an instruction. INSTRUCTION – RSLogix’s command language is comprised of “instructions”. Let’s take a quick look at how memory locations (including hardware I/O) are accessed with RSLogix 500. There are a number of addressing schemes used by PLC manufacturers.