Posted 5 Oct 2020 Dear Engineerds, My Master (non siemens) doesn't see the Holding Registers of the Slave (S7-1200) plc. However the Q coils are fine and all Diagnostics don't show errors. The Hardware: S7-1200 – CPU 1215C CM PtP – CB1241 RS485 (6ES7 241-1CH30-1XB0) - Half Duplex RS584 Firmware: Modbus_Comm_Load (V3.1) Modbus_Slave (V4.0) I've tried with various DB, UDTs and manipulating HR_Start_offset parameter with no success. Could you advise what am I possibly missing? Modbus_Comm_Load_DB_Snapshot.xlsx Modbus_Slave_DB_Snapshot.xlsx Share this post Link to post Share on other sites
Posted 6 Oct 2020 which DB you have created for Slave Registers and how did you linked it to MODBUS_Slave Block. Please provide screenshot of it 1 person likes this Share this post Link to post Share on other sites
Posted 6 Oct 2020 Dear Ragib, I've attached the files below. Please keep in mind I've tried with different data blocks, I've tried with Custom UDTs, Tried with Array of Int, Word etc. I noticed that other working projects use Modbus_Comm_Load V2.1 and Modbus_Slave V2.1 could this be an issue? Share this post Link to post Share on other sites
Posted 6 Oct 2020 Answer: CB1241//CM1241 modules are legacy modules which use old version of modbus instructions (ver 2.1) Share this post Link to post Share on other sites