# Direct PLCTag from one machine to another machine?

**URL:** <https://forum.inductiveautomation.com/t/direct-plctag-from-one-machine-to-another-machine/3439>\
**Category:** Ignition\
**Created:** [October 14, 2011, 10:16pm UTC](https://forum.inductiveautomation.com/t/direct-plctag-from-one-machine-to-another-machine/3439 "2011-10-14T22:16:59Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![bachphi](https://avatars.discourse-cdn.com/v4/letter/b/ccd318/32.png) [@bachphi](https://forum.inductiveautomation.com/u/bachphi)\
**Post date:** [October 14, 2011, 10:16pm UTC](https://forum.inductiveautomation.com/t/direct-plctag-from-one-machine-to-another-machine/3439/1 "2011-10-14T22:16:59Z")

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Hi,  
here is my scenario:  
I have two PLC machines, machine#1 has a CycleOvertime bit that I want to send it to the Ignition gateway, then the gateway would let machine #2 know about this condition and give an indicator output.

Thanks in advance.

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**Author:** ![Travis.Cox](https://avatars.discourse-cdn.com/v4/letter/t/b9bd4f/32.png) [@Travis.Cox](https://forum.inductiveautomation.com/u/Travis.Cox)\
**Post date:** [October 14, 2011, 10:32pm UTC](https://forum.inductiveautomation.com/t/direct-plctag-from-one-machine-to-another-machine/3439/2 "2011-10-14T22:32:56Z")

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You can accomplish that in one of three ways:

1. Create a DB expression tag with an expression that returns PLC 1’s tag value and writes it to PLC 2’s tag

2. Create a standard transaction group to do the same as 1.

3. Use a gateway tag change script to write from one PLC to another.

The first option will probably be the easiest.

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**Author:** ![bachphi](https://avatars.discourse-cdn.com/v4/letter/b/ccd318/32.png) [@bachphi](https://forum.inductiveautomation.com/u/bachphi)\
**Post date:** [October 15, 2011, 2:40am UTC](https://forum.inductiveautomation.com/t/direct-plctag-from-one-machine-to-another-machine/3439/3 "2011-10-15T02:40:44Z")

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lol, Travis, i have more than one option! I cant even figure one out.

I created a new DBtag , MyDBTag, with this expression  
{[.]Ack\_bit}={[~]PLC1/CycleOvertime\_bit}

What did I do wrong here?

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**Author:** ![Travis.Cox](https://avatars.discourse-cdn.com/v4/letter/t/b9bd4f/32.png) [@Travis.Cox](https://forum.inductiveautomation.com/u/Travis.Cox)\
**Post date:** [October 17, 2011, 3:39pm UTC](https://forum.inductiveautomation.com/t/direct-plctag-from-one-machine-to-another-machine/3439/4 "2011-10-17T15:39:58Z")

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A single equals in the expression language is just equality not assignment. Look to the bottom of the expression tab and you will see a write-back section. There you can select the tag you want to write the above expression to.

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**Author:** ![bachphi](https://avatars.discourse-cdn.com/v4/letter/b/ccd318/32.png) [@bachphi](https://forum.inductiveautomation.com/u/bachphi)\
**Post date:** [October 17, 2011, 5:04pm UTC](https://forum.inductiveautomation.com/t/direct-plctag-from-one-machine-to-another-machine/3439/5 "2011-10-17T17:04:17Z")

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I already tried the write back method like you suggested even before I tried that equal expression.

Anyway, just talked to Bob in support, I need to upgrade mine from v7.3 to v7.3.1 to get it work.

However creating a standard transaction group method does work on v7.3