# WagoAppPowerMeasurement sample app Unresolved reference when using 750-494 function blocks

**URL:** <https://www.wago.community/t/wagoapppowermeasurement-sample-app-unresolved-reference-when-using-750-494-function-blocks/1310>\
**Category:** CODESYS\
**Tags:** edge-controller\
**Created:** [November 7, 2024, 3:49pm UTC](https://www.wago.community/t/wagoapppowermeasurement-sample-app-unresolved-reference-when-using-750-494-function-blocks/1310 "2024-11-07T15:49:28Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![czek](https://avatars.discourse-cdn.com/v4/letter/c/848f3c/32.png) [@czek](https://www.wago.community/u/czek)\
**Post date:** [November 7, 2024, 3:49pm UTC](https://www.wago.community/t/wagoapppowermeasurement-sample-app-unresolved-reference-when-using-750-494-function-blocks/1310/1 "2024-11-07T15:49:28Z")

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After successful build I get the following error message when downloading:  
[FATAL ERROR] Unresolved reference: ‘FUIODRVCALCULATESLOTNUMBER’

Configuration:  
CODESYS V3.5 SP19 Patch 7  
WAGO Edge Controller 752-8303/8000-0002 FW27  
Field bus coupler 750-362  
3-Phase Power Measurement 750-494

Implementation is copied from Sample Project WagoAppPowerMeasurement\_Example\_04.project but that was created in Patch 2. The project will compile and run when I exclude from build the code for WagoFieldbusModule.FbModule\_75x\_494. Please advise on library requirements for 750-494 fieldbus implementation.

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**Author:** ![czek](https://avatars.discourse-cdn.com/v4/letter/c/848f3c/32.png) [@czek](https://www.wago.community/u/czek)\
**Post date:** [November 7, 2024, 4:10pm UTC](https://www.wago.community/t/wagoapppowermeasurement-sample-app-unresolved-reference-when-using-750-494-function-blocks/1310/2 "2024-11-07T16:10:36Z")

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Update:  
I was able to resolve this by Uninstalling all versions of WagoSysKbusTerminalControl\_Internal\_Common and WagoSysKbusTerminalControl\_Internal\_PFC  
through the Library Repository.

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**Author:** ![Alexander\_Landfried](https://sea2.discourse-cdn.com/flex016/user_avatar/www.wago.community/alexander_landfried/32/306_2.png) [@Alexander\_Landfried](https://www.wago.community/u/Alexander_Landfried)\
**Post date:** [November 11, 2024, 9:13am UTC](https://www.wago.community/t/wagoapppowermeasurement-sample-app-unresolved-reference-when-using-750-494-function-blocks/1310/3 "2024-11-11T09:13:48Z")

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@czek

Did you have some previous Codesys Versions installed on your System?

Please ensure you installed Codesys V3.5.19.7 with separated Repositorys.

 ![image](https://us1.discourse-cdn.com/flex016/uploads/wago/original/2X/1/1efb5e39575f5db30615d701bf722561d6562c34.png)

You can watch this Tutorial:  
[Tutorials CODESYS | WAGO Download Center](https://downloadcenter.wago.com/wago/learning-material/details/lyh0o9t0afu3ir2wwkb)

since FW27 we support 64bit Operating Systems (for new PFC300 and the Virtual Control for our Edge Computers)

That might lead to issues if you don’t install with separate Repositorys.

 ![image](https://us1.discourse-cdn.com/flex016/uploads/wago/original/2X/5/5ca42cbadec4c7bf526c36a9da6c2e8c97c326af.jpeg)

Hope this helps.

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<div class="post-metadata">

**Author:** ![czek](https://avatars.discourse-cdn.com/v4/letter/c/848f3c/32.png) [@czek](https://www.wago.community/u/czek)\
**Post date:** [January 27, 2025, 8:24pm UTC](https://www.wago.community/t/wagoapppowermeasurement-sample-app-unresolved-reference-when-using-750-494-function-blocks/1310/4 "2025-01-27T20:24:48Z")

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This project was migrated from E!Cockpit and at one time used a PFC200. This error was generated after migrating. Upon further review I found it could be resolved as well by setting the placeholder to ‘WagoSysKbusTerminalControlInternal’ to none:

 ![image](https://us1.discourse-cdn.com/flex016/uploads/wago/original/2X/c/c0a6b55ef73a50d18e9867742275f15f6033a617.png)