MODBUS RTU is a widely adopted communication protocol in industrial automation, known for its simplicity, reliability, and efficiency. Leveraging the robustness of RS485 serial communication, it enables seamless interaction between multiple slave devices and a central master in a multi-drop network. This implementation focuses on the integration of MODBUS RTU Slave functionality on STM32 microcontrollers, utilizing minimal code space while ensuring reliable real-time data exchange. Key components include the MODBUS memory model, frame structure, and essential function codes for reading and writing data. Practical testing is facilitated through simulation tools like Simply Modbus Master, and real-world applications are demonstrated using STM32-based hardware. The approach provides a scalable and cost-effective solution for embedded systems requiring industrial-grade communication.