# Modbus addressing issue

**URL:** <https://forum.inductiveautomation.com/t/modbus-addressing-issue/98280>\
**Category:** Ignition\
**Tags:** perspective, modbus\
**Created:** [November 6, 2024, 2:40pm UTC](https://forum.inductiveautomation.com/t/modbus-addressing-issue/98280 "2024-11-06T14:40:57Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Nestor\_Bjorck](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nestor_bjorck/32/69406_2.png) [@Nestor\_Bjorck](https://forum.inductiveautomation.com/u/Nestor_Bjorck)\
**Post date:** [November 6, 2024, 2:40pm UTC](https://forum.inductiveautomation.com/t/modbus-addressing-issue/98280/1 "2024-11-06T14:40:57Z")

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Hi!

I am trying to add an OPC tag pointing to a Modbus Coil. From reading the manual I understood that the "OCP Item Path" is specified as such:

[OPC-DeviceName]Tagtype + Address

In my case: [temp]C3011

When using this syntax, the tag returns the fault:  
_"Bad\_NotConnected: The variable should receive its value from another variable"_

The gateway has a connection to the modbus-device, and the specified address is set up on this external device. I am using "Modbus RTU over TCP" for the device connection.

What are the possible reasons for this error-code?

BR, Nestor.

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<div class="post-metadata">

**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:** [November 6, 2024, 2:44pm UTC](https://forum.inductiveautomation.com/t/modbus-addressing-issue/98280/2 "2024-11-06T14:44:21Z")

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You're probably getting no response from the device and then the "reconnect after consecutive timeouts" setting is forcing a reconnect.

Are you sure that's the right driver type? Have you tried specifying a non-zero unit id, e.g. `[temp]1.C3011`?

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<div class="post-metadata">

**Author:** ![Nestor\_Bjorck](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nestor_bjorck/32/69406_2.png) [@Nestor\_Bjorck](https://forum.inductiveautomation.com/u/Nestor_Bjorck)\
**Post date:** [November 6, 2024, 2:58pm UTC](https://forum.inductiveautomation.com/t/modbus-addressing-issue/98280/3 "2024-11-06T14:58:31Z")

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I had issues using the "Modbus TCP" protocol, where it would reconnect from the gateway consistently. I did however believe this to be because the device never pointed to any address, causing it to go "Inactive". Does the "Connected" mark in the gateway not mean that it's receiving data from the device?

The device is set up to to force reconnects.

The Modbus device is specified to have the possibility of using both RTU and TCP.

When trying "[temp]1.C3011", I get the error-code:  
"Bad\_ConfigurationError: There is a problem with the configuration that affects the usefulness of the value."

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<div class="post-metadata">

**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:** [November 6, 2024, 2:59pm UTC](https://forum.inductiveautomation.com/t/modbus-addressing-issue/98280/4 "2024-11-06T14:59:57Z")

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> [@Nestor\_Bjorck](#):
>
> Does the "Connected" mark in the gateway not mean that it's receiving data from the device?

No, it only means a TCP connection was opened.

> [@Nestor\_Bjorck](#):
>
> When trying "[temp]1.C3011", I get the error-code:  
> "Bad\_ConfigurationError: There is a problem with the configuration that affects the usefulness of the value."

Do you have an address map defined or something? Are you sure there's no spaces or other characters in your OPC Item Path? It looks correct for a Modbus address.

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<div class="post-metadata">

**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:** [November 6, 2024, 3:01pm UTC](https://forum.inductiveautomation.com/t/modbus-addressing-issue/98280/5 "2024-11-06T15:01:12Z")

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If you have some other software (Modpoll, etc...) that can connect and read data then a Wireshark comparison can help figure out the difference.