# Use script code with comunication Modbus TCP/IP in UR3 with CB3 **URL:** \ **Category:** URScript\ **Created:** [February 20, 2025, 9:14am UTC](https://forum.universal-robots.com/t/use-script-code-with-comunication-modbus-tcp-ip-in-ur3-with-cb3/38674 "2025-02-20T09:14:09Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![mcobos](https://avatars.discourse-cdn.com/v4/letter/m/dbc845/32.png) [@mcobos](https://forum.universal-robots.com/u/mcobos)\ **Post date:** [February 20, 2025, 9:14am UTC](https://forum.universal-robots.com/t/use-script-code-with-comunication-modbus-tcp-ip-in-ur3-with-cb3/38674/1 "2025-02-20T09:14:09Z")
Good morning, I am new to using scripts and I am using them to control a Festo servomotor. To do this, I am trying to implement the examples shown here for the CMMT-AS model: > **[ModbusExamples/festo-cmmt-as at main ยท UniversalRobots/ModbusExamples](https://github.com/UniversalRobots/ModbusExamples/tree/main/festo-cmmt-as)** > > Example programs, and URScript snippets for Modbus communication, - UniversalRobots/ModbusExamples The main problem I have encountered is that when executing the example code the compiler returns several failures in the basic functions of modbus: modbus\_add\_rw\_signal modbus\_get\_error In them tells me that they do not exist. I hope someone can help me with the failure and maybe I need to do some previous load of some library. Thank you very much. ---
**Author:** ![robin\_gdwl](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.universal-robots.com/robin_gdwl/32/2676_2.png) [@robin\_gdwl](https://forum.universal-robots.com/u/robin_gdwl)\ **Post date:** [February 20, 2025, 5:47pm UTC](https://forum.universal-robots.com/t/use-script-code-with-comunication-modbus-tcp-ip-in-ur3-with-cb3/38674/2 "2025-02-20T17:47:39Z")
> [@mcobos](#): > > modbus\_add\_rw\_signal This function might only exist for e-series robots. I can not find it in the script reference for CB-Robots (3.15)