Syncronising two variables

[Veganic 8]

I have a variable, A. I want to be able to edit this variable in two places, X and Y. X and Y are connected by CC link. How do I do it? Edit : I meant synchronising Edited 25 Mar 2010 by Veganic

[Inntele 60]

Hi, I did solve the similar task for Profibus-DP network. It can be done with "change" bit which has to be set simultaneously with change of variable value. The specific decision depends on type of X and Y remote device (an example, HMI is connected directly to CC-Link or HMI is connected to network via PLC, etc).

[Veganic 8]

So it can be done! How is the "change bit" reset after updating the variable? Would the following work? The system is HMI <-> Q plc <- CC link-> FXplc <-> HMI. DY from Q to DX in FX. DY from FX to DX in Q. Change D on HMI. FX monitors the difference between D and DY and/or DX. DY in FX is updated and change bit is set. Q recieves the change bit and sets DY = DX and D on HMI = DY. Q sends "change accepted" bit. FX resets the "change bit" on receiving the "change accepted" bit. Q reset the "change accepted" bit when the "change bit" goes off. All registers should now have the same value. Repeat for the Q plc and decide that if both are changed at the same time the Q takes precedence!

[Inntele 60]

Some not. This bit breaks the connection between the DX and DY in the PLC, which made dubbing (PLC1) and prohibits the change of variable from HMI in the opposite controller until the cycle DY-DX-DY-DX is not finished and DX will be equal again to DY in PLC1. Thus no one PLC will not have priority.

[Veganic 8]

Like this? Q plc: [<> Dhmi Dx]---(Qchange) Qchange -|\|-[Mov Dx Dy] Qchange -| |-[Mov Dhmi Dy] FXchange -| |-[Mov Dx Dhmi] ----------------------------------------------------- FX plc: [<> Dhmi Dx]---(FXchange) FXchange -|\|-[Mov Dx Dy] FXchange -| |-[Mov Dhmi Dy] Qchange -| |-[Mov Dx Dhmi] ------------------------------------------------------- And inhibit changes on HMIs as necessary.

[Inntele 60]

You can do without Dhmi and "tie" the value in HMI to DY directly. Also you can use "off" active state of change bit, because initially the variable value must be synchronized with one of PLC: An example, the initial sinchronization with Q. Set Change bit in FX (change is absent) DY Q --> DX FX --> DY FX --> DX Q If DX Q = DY Q set Change bit in Q. When new value is being written from HMI, simultaneously the appropriate bit must be reset from this HMI (without PLC program code!). Edited 25 Mar 2010 by Inntele

[Veganic 8]

So I think it becomes: Q plc: [<> Dy Dx]---(Qchange) Qchange -|\|-[Mov Dx Dy] ----------------------------------------------------- FX plc: [<> Dy Dx]---(FXchange) FXchange -|\|-[Mov Dx Dy] ------------------------------------------------------- And inhibit changes on HMIs as necessary.

[Inntele 60]

Veganic, see information which was added in my previous post. In each PLC must be following: = DX DY OR First Scan (M8002 for FX, SM402 for Q) SET Change Bit Edited 25 Mar 2010 by Inntele

[Veganic 8]

I haven't tried it yet but I think I've over-simplified the problem. Without Dhmi I can't discrimiate between a change in Dx and a change in DY. It will work if I set "change bit" in the HMI simutaneously, as you suggest, but how? A macro?

[Inntele 60]

I don't know, what HMI do you use (from Beijer or from Mitsubishi, or from the third party). For E-series/E1000-series it may be to do either without macro (this is typical function for tag in E-designer), or with macro.

[Veganic 8]

E1000 sereis.

[Inntele 60]

Sorry. I've checked, unlike E-Designer v7.20, where I did it, in v7.50 is impossible to set/reset/momentary a bit only according to input of new value. Therefore now is need to organize it in PLC.

[Veganic 8]

Thanks, I think I have the solution now.

[Inntele 60]

OK. I also think, it is time to move from words to deeds