# Read and write from different addresses

**URL:** <https://forum.inductiveautomation.com/t/read-and-write-from-different-addresses/52245>\
**Category:** Ignition\
**Created:** [October 22, 2021, 1:25pm UTC](https://forum.inductiveautomation.com/t/read-and-write-from-different-addresses/52245 "2021-10-22T13:25:08Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![spm](https://avatars.discourse-cdn.com/v4/letter/s/7ea924/32.png) [@spm](https://forum.inductiveautomation.com/u/spm)\
**Post date:** [October 22, 2021, 1:25pm UTC](https://forum.inductiveautomation.com/t/read-and-write-from-different-addresses/52245/1 "2021-10-22T13:25:08Z")

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Hello,  
I am using Modbus RTU over TCP through the OPC interface of course. I cannot see an easy way to setup reading from one address and writing to another. The only thing I found was using the OPC tag write and putting in the write address specifically for each write tag.

Is there a better way to specify the read vs. the write address when they are different? That seems very tedious and clunky to do it that way.

Thanks for your help,  
Steve

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**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [October 22, 2021, 1:28pm UTC](https://forum.inductiveautomation.com/t/read-and-write-from-different-addresses/52245/2 "2021-10-22T13:28:46Z")

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No, this is a pretty uncommon scenario and not supported directly in the tag system.

I’d set up a tag for the read address, make it read only in Ignition as well if it’s not already read only in Modbus by virtue of being an Input Register or Discrete Input, and then any time you need to write just do it via script with `system.opc.writeValue`.

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**Author:** ![spm](https://avatars.discourse-cdn.com/v4/letter/s/7ea924/32.png) [@spm](https://forum.inductiveautomation.com/u/spm)\
**Post date:** [October 22, 2021, 1:40pm UTC](https://forum.inductiveautomation.com/t/read-and-write-from-different-addresses/52245/3 "2021-10-22T13:40:31Z")

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OK. I thought as much. Thanks for quick response.  
Steve