# Modbus tcp error

**URL:** <https://discourse.nodered.org/t/modbus-tcp-error/47026>\
**Category:** General\
**Created:** [11 June 2021 11:55 UTC](https://discourse.nodered.org/t/modbus-tcp-error/47026 "2021-06-11T11:55:09Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![jorge7](https://avatars.discourse-cdn.com/v4/letter/j/a587f6/32.png) [@jorge7](https://discourse.nodered.org/u/jorge7)\
**Post date:** [11 June 2021 11:55 UTC](https://discourse.nodered.org/t/modbus-tcp-error/47026/1 "2021-06-11T11:55:10Z")

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Hello,

I am trying to read data from Modbus tcp but I receive this error:

"Error: Modbus exception 3: Illegal data value (value cannot be written to this register)"

Thanks and regards.

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**Author:** ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)\
**Post date:** [11 June 2021 12:06 UTC](https://discourse.nodered.org/t/modbus-tcp-error/47026/2 "2021-06-11T12:06:54Z")

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You say you are trying to read data but the error suggests you are trying to write data.

Are you trying to write to a read-only address or an address that does not exist?

Have you tried reading simple registers that you definitely know exist?

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**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [10 August 2021 12:06 UTC](https://discourse.nodered.org/t/modbus-tcp-error/47026/3 "2021-08-10T12:06:55Z")

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