Siemens PLC Programming Using SCL with MODBUS - Part 03

Describe the physical wiring for Modbus on an S7-1200 with the CB1241 card, including ta-ta to tr minus, tb-trv to tr plus, and USB-RS485 connectivity to a PC.

Configure Siemens S7-1200 hardware for Modbus, enable clock and system memory, set Modbus card parameters, verify IP connectivity, and download the project.

Configure the mb_comm_load library to enable Modbus RTU communication by setting the port to 269, baud rate 9600, parity none, and a 1000 milliseconds timeout, establishing a Modbus master link.

Configure the modbus master with mm master and mm com law, defining the port and slave id, then create an mb config read block to map data to a buffer.

Explore reading five Modbus slave IDs on a Siemens S7-1200 using SCL and Modbus RTU, building data blocks, and automating Modbus address cycling.

Test Modbus RTU between an S7-1200 master and slaves using MB master DB; configure port, baud, parity, and addresses; read holding register from 40101 with length 20 and monitor results.

Map data from five Modbus slave IDs to five energy meters using a case statement in SCL, storing read data into dedicated data blocks and preparing for HMI access.

Configure the mb_master for write operations to a Modbus slave by creating a write data block, setting the data address and length, and updating the mb config.

Test Modbus write data by configuring RTU write operations, data address 40201 and length, and verify data transfer to multiple slave IDs and back to an external program.