In RSLOGIX 500 is there any reason why that you can't turn on several outputs in one rung by using branches.

Thanks,
bowler

Should work. Are you having a problem? If so post your code we will take a look.

Of course this is legitamate in all RSLogix programs.
You may have something else overwriting the outputs that don't appear to be working.
No way to tell unless you post your code for us to look at.

In Rslogix 500 you cannot used the same real output address in OTE. it should only be used once otherwise their were coflict on their logic, But you can used it many time as long as it used as input data or XIC or XIO.

No problem with multiple outputs on separate branches. In fact, it is common to see a branch and two outputs where one controls a pilot light ("output ON") and the other controls the actual output relay for a device. I also like to use a soft bit (Bx/x) as the outputs for operator displays because then if you decide to change the logic, you don't have to mess with the operator display, just like you can with a pilot light that isn't hardwired to a starter.

If your goal is to trigger multiple outputs on the SAME word, you can treat the output as a word instead of a set of bits. Then you can use MOV to write several bits at once, or masked moves if your processor supports them to selectively turn on/off individual bits. The logic is not necessarily pretty but you can do up to 16 bits at once this way as long as they are located in the same word...sometimes having huge branch instructions is harder to read than a single masked move.


Partly true. And there may be places to do this. However, it is frequently a dircet indicator of a bug. If you have multple OTE instructions on the SAME bit in the SAME code executing "simultaneously", the last one executed will be the only one that matters (the others are overwritten). This is because the PLC sequence of events is to do I/O, scan the ladder, then do I/O, etc. If the SLC supports SFC's (the PLC-5 does), then you will FREQUENTLY find multiple OTE's because not all ladders may be active depending on the state of the SFC. Another example where you might see some of this is if you make use of MCR zones. I'm not really a fan of MCR zones mostly because they frequently make the code harder to read and debug, but they have their place sometimes. That being said, it's not very clean (since the logic should simply be located entirely outside the MCR zone) but I've seen multiple OTE's with the same input conditions where one is inside an MCR zone and one is located outside of it to override the output when the MCR zone triggers.

In a ControlLogix, multiple OTE commands on the same real output are a real problem because on that platform, I/O and ladder scans are asynchronous to each other...you can't really ever tell which state the output would be in.

Another frequent place that you may see multiple output instructions on the same bit is with OTL and OTU. In fact, you may even see all 3 (OTE/OTU/OTL) intermixed. Why? For instance, it may make the code cleaner if you have an OTU in a rung following an OTE where the OTU represents an "override" command. Again, not a good idea with ControlLogix but it's not uncommon in PLC-5 & SLC.