# How Ignition differentiate tags created from PLC with same registers? **URL:** \ **Category:** Ignition\ **Created:** [August 1, 2019, 9:23am UTC](https://forum.inductiveautomation.com/t/how-ignition-differentiate-tags-created-from-plc-with-same-registers/27074 "2019-08-01T09:23:48Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![miculacristianradu](https://avatars.discourse-cdn.com/v4/letter/m/b782af/32.png) [@miculacristianradu](https://forum.inductiveautomation.com/u/miculacristianradu)\ **Post date:** [August 1, 2019, 9:23am UTC](https://forum.inductiveautomation.com/t/how-ignition-differentiate-tags-created-from-plc-with-same-registers/27074/1 "2019-08-01T09:23:48Z")
Hello guys, I want to add 2 new same PLC’s to our plant, and they are both same model. The first step is as I read to add the devices in Ignition Gateway. But my question is how Ignition can differentiate the tags from tempreture created for these 2 locations with same PLC and same tags? ![pic1](https://us1.discourse-cdn.com/inductiveautomation/original/2X/e/ea3382b376b7f1c94e9a01f656a44dcc674275c6.png) - screenshot from Gateway ![pic2](https://us1.discourse-cdn.com/inductiveautomation/original/2X/e/e564b5d94d0bbf748ca18a6b19b10e4d90ceed9b.png) - screenshot from Ignition designer Thank you! ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [August 1, 2019, 11:12am UTC](https://forum.inductiveautomation.com/t/how-ignition-differentiate-tags-created-from-plc-with-same-registers/27074/2 "2019-08-01T11:12:18Z")
In the OPC Item Path, the beginning part in square brackets must name the device. When using UDT parameters as shown, the parameter `IdPT` must be either 411 or 413 to yield a proper device name. And thereby select which PLC is the target. ---
**Author:** ![miculacristianradu](https://avatars.discourse-cdn.com/v4/letter/m/b782af/32.png) [@miculacristianradu](https://forum.inductiveautomation.com/u/miculacristianradu)\ **Post date:** [August 1, 2019, 11:34am UTC](https://forum.inductiveautomation.com/t/how-ignition-differentiate-tags-created-from-plc-with-same-registers/27074/3 "2019-08-01T11:34:55Z")
![ex2](https://us1.discourse-cdn.com/inductiveautomation/original/2X/e/e17f99af42d33463c32121cf983cc9e0fe4097db.png) Hi, I now understand the part with IdPT, it is show in the parameters list of the UDT, but also AdresaModbus is shown in the parameters list, but I notice that the address of the parameter is 1 for all the UDT’s. (see screenshots bellow) ![ex1](https://us1.discourse-cdn.com/inductiveautomation/original/2X/b/b8f856cc99a362f40b01b6a6ef4321280d4621d3.png) Is that normal? What kind of address I need to put in the parameters list for the AdresaModbus exactly? Thank you! ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [August 1, 2019, 11:47am UTC](https://forum.inductiveautomation.com/t/how-ignition-differentiate-tags-created-from-plc-with-same-registers/27074/4 "2019-08-01T11:47:12Z")
It depends on the device. When using serial Modbus, that allows you to address different nodes on the same link. With Modbus TCP, it is typically 0 or 1. With Modbus TCP to Modbus serial gateways, the address is typically passed through. ---
**Author:** ![miculacristianradu](https://avatars.discourse-cdn.com/v4/letter/m/b782af/32.png) [@miculacristianradu](https://forum.inductiveautomation.com/u/miculacristianradu)\ **Post date:** [August 1, 2019, 11:53am UTC](https://forum.inductiveautomation.com/t/how-ignition-differentiate-tags-created-from-plc-with-same-registers/27074/5 "2019-08-01T11:53:02Z")
Thank you very much for your explanation!