Time synchronization

tgaljar · Jul 24, 2006

Hi,

One question about time synchronization: what is the best way to synchronize time on 6 controllers in the same DH485 network one slc 500 and 5 micrologix1200 with RTC module? I've tried to MSG time addresses from SLC500 to RTC address in micrologix but that doesn’t work!

Thanks!

rdrast · Jul 24, 2006

I hate to ask, but why do you need those PLC's to be time synchronous?

I suppose, if I absolutely needed the RTC'S in that group of PLC's to be (almost, but never exactly) time synchronized, I'd use an HMI as the master, running a script in the background to update all the clocks every minute or so.

How accurate must you be? DH485 isn't a speed demon, and depending on network traffic, you could be off by many seconds (or minutes) if you don't time your update with more precision than I think you can.

Hydro Power Guy · Jul 24, 2006

I am not sure if your needs are this severe, but just in case....

Sequence of events level of time synchronization requires a GPS signal to sync the clocks of the equipment. Hiprom (encompass partner) makes PLC 5, SLC and Control Logix modules to provide this function.

http://www.hiprom.com/products.htm

tgaljar · Jul 24, 2006

They don't need to be so accurate just to turn the light on and reset some bits in midnight. I thought to sync them every half an hour.

What kind of script are you talking about, and how to use it? I found some tool from Rsview for time sync but it sets tome correctly only for SLC but it doesn’t work on micrologix!

There are two SCADA computers for supervision in the same network so one of them could run script!

The PLCs came with RTC modules so I thought to use them.

rsdoran · Jul 24, 2006

Special notes about writing to RTC function files

Local File Address

When MSGing to/from Real Time Clock Function Files in MicroLogix 1200 Series B and C, MicroLogix 1500 LSP Series B and C, or MicroLogix 1500 LRP Series B and C processors:

* The Local File Address can only address the Real Time Clock (RTC) function file by the programming software when using Target Device Type 500CPU.
* The Local File Address can only address the RTC function file in a MSG Write instruction by the programming software when the Target File Address targets an RTC file.
* The Local File Address can only address the RTC function file in a MSG Write instruction by the programming software when the Target File Address targets an integer file.

Target File Address
When MSGing to/from Real Time Clock Function Files in the MicroLogix 1500 LRP Series B and C Processor:

* The Target File Address can only address a Real Time Clock (RTC) function file by the programming software when using Target Device Type 500CPU.
* When the Local File Address targets the RTC file, the Target File Address can only address an RTC function file in a MSG Write Instruction or an integer data file in a MSG Write instruction by the programming software.

RSLogix 500 - Copyright Rockwell Software 2000, 2001

Technically since they are real time clocks they should stay fairly accurate for a long time after being set. You can synchronize them one at a time to your computers time and they all should be the same.

Time synchronization

tgaljar

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rdrast

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Hydro Power Guy

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tgaljar

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rsdoran

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