# Modbus RTU C70

**URL:** <https://community.br-automation.com/t/modbus-rtu-c70/4391>\
**Category:** Controls & Vision\
**Tags:** modbus\
**Created:** [September 24, 2024, 7:13pm UTC](https://community.br-automation.com/t/modbus-rtu-c70/4391 "2024-09-24T19:13:51Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Austin\_Moodley](https://avatars.discourse-cdn.com/v4/letter/a/FF8800/32.png) [@Austin\_Moodley](https://community.br-automation.com/u/Austin_Moodley)\
**Post date:** [September 24, 2024, 7:13pm UTC](https://community.br-automation.com/t/modbus-rtu-c70/4391/1 "2024-09-24T19:13:51Z")

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Hello everyone, having decent experience with modbus tcp and b&r plcs i would like to attempt a modbus rtu connection to a slave module .  
With tcp it is relatively simple to use the Ethernet interface and configure a slave or master connection.  
Can anyone assist in also using a simple method to use modbus rtu and achieve this simple method ie read write coils,registers and so on

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**Author:** ![alexander.hefner](https://dub1.discourse-cdn.com/brcommunity/user_avatar/community.br-automation.com/alexander.hefner/32/111_2.png) [@alexander.hefner](https://community.br-automation.com/u/alexander.hefner)\
**Post date:** [September 24, 2024, 7:45pm UTC](https://community.br-automation.com/t/modbus-rtu-c70/4391/2 "2024-09-24T19:45:14Z")

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Hi,

there’s a library called [DRV\_mbus](https://help.br-automation.com/#/en/4/libraries/drv_mbus/fbks/fbks_drv_mbus.html) for master or slave functionality, some more Infos can be found here:

> [@Modbus Register Addressing for variables](https://community.br-automation.com/t/modbus-register-addressing-for-variables/4099/2):
>
> Hi, if I got it right and you’re using modbus serial on one of the “normal” serial interfaces of the PLC, then the’re no address assign by tag editors. In that case, the Modbus RTU protocol is processed by own code using library “[DRV\_mbus](https://help.br-automation.com/#/en/4/libraries/drv_mbus/fbks/fbks_drv_mbus.html)”. How to put/get modbus data (coils, registers) into process variables depends on if you’re a modbus master or a slave. Being a master, the configuration is done by settings in the configuration data module that has to be used together with the function bl…

Best regards!

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<div class="post-metadata">

**Author:** ![Austin\_Moodley](https://avatars.discourse-cdn.com/v4/letter/a/FF8800/32.png) [@Austin\_Moodley](https://community.br-automation.com/u/Austin_Moodley)\
**Post date:** [September 25, 2024, 5:41am UTC](https://community.br-automation.com/t/modbus-rtu-c70/4391/3 "2024-09-25T05:41:35Z")

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Thank you will try out this library!