Scan Counting

bobby111 · Aug 8, 2006

I need to try to count PLC scans with an allen bradly SLC processor. If anyone could help me out it would be much appreciated.

Bobby

TimWilborne · Aug 8, 2006

Put an unconditional ADD instruction. Source a your scan tag, Source b 1, and destination you scan tag.

You will have to deal with the rollover. Which SLC you got?

bobby111 · Aug 8, 2006

slc 5/04

panic mode · Aug 8, 2006

what exactly you want to achive by counting scans?
measure scan time of the plc? you can simply read register
since this is already calculated by cpu. default is to show
values in 10ms increments but toggling bit S:33/9 will
change it to 1ms resolution.

bobby111 · Aug 8, 2006

How do I make a scan tag?

bobby111 · Aug 8, 2006

I need to turn on a bit every X scans

TimWilborne · Aug 8, 2006

I just meant point to a data file

How many scans between this output?

If it is less than 32767 then just use an integer and a compare statement.

More than that and you need to setup something to count how many times it hits a certain value and then do the math to compare the value.

Why do you need to turn on a bit every so many scans. Curious about the application. Can't say I have ever seen this

TConnolly · Aug 8, 2006

bobby111 said:
I need to turn on a bit every X scans

Then use an unconditonal counter and unlatch the /CU bit so that it will count continuously. The CU bit is what the counter uses so it only up counts on a false to true rung transtion. Unlatching the CU bit makes the counter run continuously. This way the CTU instruction will do all of the adding and comparing for you. With a CTU, you also wont have to worry about integer roll over and the minor error bet set by rolloever.



 -----------+----+-CTU-------+-(CU)-

            |    | C5:0      |

            |    | PRE    X  +-(DN)-

            |    | ACC    0  |

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

            |

            |             C5:0/CU

            +--------------(OTU)---

          

     C5:0/DN                BIT

 -----] [-------+----------(OTE)---

                |

                |          C5:0

                +----------(RES)---

rsdoran · Aug 9, 2006

Why would a bit (output) be based on scan time?

Scan Counting

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