# Writing negative value to register via modbus tcp/ip

**URL:** <https://discourse.nodered.org/t/writing-negative-value-to-register-via-modbus-tcp-ip/58976>\
**Category:** General\
**Tags:** modbus\
**Created:** [25 February 2022 09:52 UTC](https://discourse.nodered.org/t/writing-negative-value-to-register-via-modbus-tcp-ip/58976 "2022-02-25T09:52:45Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![peterr](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/peterr/32/57583_2.png) [@peterr](https://discourse.nodered.org/u/peterr)\
**Post date:** [25 February 2022 09:52 UTC](https://discourse.nodered.org/t/writing-negative-value-to-register-via-modbus-tcp-ip/58976/1 "2022-02-25T09:52:45Z")

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Hi,  
I'm trying to get my inverter to charge battery from grid thru modbus tcp/ip.  
I finally got an answer from Fronius support, what values to which registers I need to write.  
Writing to single registers works fine, but I have difficulties in figuring out two things:

1. How do I write a Negative value (-5000) to a register?
2. How do I write to multiple (4) registers, that is not in a sequence right after eachother (register 40349, 40356, 40357, 40361)?

I have attached an email snip from Fronius support and the relevant register map.

![Email snip_Fronius](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/8/5/8591220d21aa0609d4edfdddfe4f3bbdec538e7f.jpeg)

 ![RegisterMap_Gen24_SF_Storage](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/9/b/9b09083dc46f2d5d6fd5e5ade169b315e63c3643.jpeg)

Ps. I'm able to write with FC16 successfully to single registers + multiple registers in a sequence (just not negative values or registers out of sequence)

Thanks in advance,  
Peter

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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:** [26 April 2022 09:53 UTC](https://discourse.nodered.org/t/writing-negative-value-to-register-via-modbus-tcp-ip/58976/2 "2022-04-26T09:53:00Z")

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