# Weird modbus write coil issue

**URL:** <https://forum.inductiveautomation.com/t/weird-modbus-write-coil-issue/5374>\
**Category:** Ignition\
**Created:** [November 4, 2012, 7:12pm UTC](https://forum.inductiveautomation.com/t/weird-modbus-write-coil-issue/5374 "2012-11-04T19:12:39Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Ikeprof](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ikeprof/32/84814_2.png) [@Ikeprof](https://forum.inductiveautomation.com/u/Ikeprof)\
**Post date:** [November 4, 2012, 7:12pm UTC](https://forum.inductiveautomation.com/t/weird-modbus-write-coil-issue/5374/1 "2012-11-04T19:12:39Z")

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I’ve attached the log file. There WILL be a lot of odd entries in it as I was trying different addressing schemes.

The symptom I am trying to figure out is when writing a ONE/true to a single memory bit location, it always throws a bad quality error. YET…it does successfully write the value. When writing a ZERO, it never throws an error. Period. Only when writing a one. I know the writes in the end are successful as the PLC program I have running is simply firing output coils based upon those memory address bits being 1 or 0 (just a protocol test ladder logic program I put together to make sure all this was working fine).

The PLC is a Hollysys LM3108 connected via a DIGI One IA, via a VPN tunnel back to ignition running at the office. Protocol is Modbus. I know…remove all the middle components to reduce/identify the potential problems (which I intend to do Monday, but in the end this will be the equipment used in this application).  
[logs.bin.gz](https://us1.discourse-cdn.com/inductiveautomation/original/2X/8/83dbe286c6a5e7b774386d9be643d54b9c7089dc.gz) (254 KB)

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<div class="post-metadata">

**Author:** ![Ikeprof](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ikeprof/32/84814_2.png) [@Ikeprof](https://forum.inductiveautomation.com/u/Ikeprof)\
**Post date:** [November 4, 2012, 7:24pm UTC](https://forum.inductiveautomation.com/t/weird-modbus-write-coil-issue/5374/2 "2012-11-04T19:24:24Z")

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Actually, ignore this post. I’m getting results that are not consistent and I don’t want to waste anyone’s time. Will open a new topic if needed.

Thank you