Posted 15 Oct 2019 Has anyone connected a Swegon ventilation unit to QJ71MB91.At Swegon, Read Holding Registers is 03 and in GX 0500. 03 is not in GX.I can't make it work. modbuscomp.pdf Share this post Link to post Share on other sites
Posted 15 Oct 2019 ok lets see you are refreshing D3000 to D3100 Holding Register 30 should go to D3000 (In you're text you're talking about holding register 3 ??) you are only reading this Device could be a +1 issue. Is communication working (no exception errors)? Share this post Link to post Share on other sites