Posted 13 Jul 2021 Hi 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. Share this post Link to post Share on other sites
Posted 30 Jul 2021 What kind of switches? Managed Ethernet switches? electrical distribution switches? Are you logging the data read via Modbus? Does the datalog show no data for when the page is closed and some data when the page is open? Share this post Link to post Share on other sites
Posted 31 Jul 2021 How often are you reading the values? Some modbus devices time out connections for inactivity in as little as ten seconds. Share this post Link to post Share on other sites
