mAcman posted a topic in HMI & SCADAHi every one. I have strange problem with Modbus communication in Citect 2018. I am communicating to the site switches through Modbus TCP protocol using MODNET driver and reading its sates. I am reading data from Input registers (registers addresses starts from 3x). In default, MODNET driver initializes communication trying conecting to holding register 40001 so I changed initialization in citect.ini to address 30001 because driver didn't want to establish connection because switches don't support holding registers. Now, connection to switches is working but only when page is open where I showing data from them. When I change the page, Citect loses communication and inform this showing alarm on HW alarm page. When I again open page where I show read data, communication back again. Where could be a problem? I will mention that I have more different Modbus TCP devices in project configured and with them don't have such problem. The only difference is that I am reading from holding registers and initialize parameter in citect.ini is not defined for them as for switches.