Micrologix Scan Bit

Hello everyone,

I was wondering if there is a "new scan cycle" bit for an AB micrologix. I know of the first scan bit. What I'm trying to do is move values to another holding registers kinda like a first in first out history. But i'd like it to do it every scan. Is there a bit that gets triggered everytime a new program scan starts?

Thanks!

Each time a rung gets executed it's a 'new scan'. (Except perhaps in a subroutine which is called from multiple points in a program.)

Thanks Bernie,

So with that said can I place a timer with preset of zero. Everytime that goes DN I can consider it as a done scan?

Just put your MOV instruction on an unconditioned rung. You do not have to have any logic in front of it.

This will move the value in N7:0 to N11:0 every scan.

|                                        |

+----------------------+-MOV----------+--+

|                      |Source    N7:0|  |

|                      |Dest     N11:0|  |

|                      +--------------+  |

If you want to see how to use a FIFO (first in first out) load and unload instruction then take a look at these examples.

http://www.plctalk.net/qanda/showthread.php?p=260919#post260919

http://www.plctalk.net/qanda/showthread.php?t=81757&highlight=FIFO

You can also use a COP instruction, but with COP you have to put your newest data at the highest address and have your oldest data at the lowest address.