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Clock Synchronization between two PLC.

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  • Clock Synchronization between two PLC.

    Hi guys. I am working with the project that involves two DL06 PLCs and can’t figure out how to synchronize the slave's PLC clock with the master one. Any help please?

  • #2
    If you can already poll the time on the master PLC, you should be able to save that time to a memory address, and then either read or write with the second PLC to get the data to it. Use the memory location to then move it into the proper memory location that the CPU time looks at.

    I personally use a BRX as my whole machine networks "master" com device. Any time I need data like time or to send logs and such I have a BRX on the network that keeps the time updated and stores log files. I use modbus to ship that data between the BRX com master and various PLCs across the warehouses. It also has instructions for easily sending data into older direct logic PLCs.
    Last edited by MikeN; 09-10-2019, 01:48 PM.


    • #3
      Use chosen communication to send a copy of the time to the slave PLC. There format the time into two V memory locations as illustrated in the CPU manual (TIME instruction). Once formatted execute the TIME instruction.



      • #4
        In the CPU manual there an example of time instruction but they use “Load Double instruction” with constant value, than outputting that value to “Out Double instruction”. My problem is that DL06 is storing the time or a day data in for memory locations. For the time it is V7747, V7766, V7767 and V7770, and for the date it is V7771, V7772, V7773 and V7774. So I don’t understand how to load the 4 memory location in one “Out Double instruction”. So what I am doing wrong. I am using “Network WX Write” instruction in the master PLC. In this instruction FROM THE MASTER - V7766, NUMBER OF BYTES -4, TO SLAVE ELEMENT – V2000. In Slave PLC I am using SP1 which is always ON to activate One- Shot instruction which contact is enabling LDD instruction V2000(reading from the master) Loading to OUTD V3000 and outputting to Time V3000. I am doing something wrong because slave PLC reading only seconds.


        • #5
          Ok guys, thanks for your help. I figured this out different way. I used LD, SHLF and ADD instructions to solve that.
          Master PLC
          STR SP4
          PD C760 (1 second clock update)
          STR C760
          LD V7770 (HOUR)
          SHLF K8
          ADD V7767 (MIN.)
          SHLF K8
          ADD V7766 (SEC.)
          OUTD V2020 (REAL TIME CLOCK)
          Then send it to slave PLC

          IN Slave PLC
          STR SP1
          PD C160
          STR C160
          LDD V2000 (Reed from master PLC)
          OUTD V2050
          TIME V2050

          Same with date update.
          Last edited by vmayak; 09-16-2019, 10:01 AM.