The EVE 200Smart PLC can utilize the Modbus RTU instruction library from Siemens software, or it can use EVE’s own UN Modbus RTU instruction library, providing users with two options. The difference between the two libraries is that Siemens’ MODBUS library is implemented in the upper-level PLC program, which is large in size, occupying almost 2KB of program space, and has lower operational efficiency. The EVE 200Smart PLC integrates the MODBUS library within the CPU, with the host computer only providing a library interface. This library interface is consistent with the original Siemens MODBUS library interface and uses the same methods. It supports most error execution codes.The specific advantages of the EVE Modbus RTU library are as follows:1. The UN Modbus library includes Modbus master and slave instructions. It supports Modbus master and slave functions on ports 0, 1, and 2 (the number of supported ports may vary by product). The storage size for the master library is 36 bytes, while the storage size for the slave library is 33 bytes.2. When using the UN Modbus library, the storage size is small, occupying less program space, making it suitable for configuration environments with high communication frequency, large data transmission volume, and the need to establish communication with multiple slaves. This effectively avoids communication failures between master and slave due to excessive communication load; it can also be applied in scenarios requiring Modbus slave communication on ports 1 and 2 (the number of supported ports may vary by product).For specific usage methods, please refer to the attachment.
UNModbusRTU Library User Manual V1.00.pdf