Decompose requests ------------------ Modbus requests and responses contain an Application Data Unit (ADU) which contains a Protocol Data Unit (PDU). The ADU is an envelope containing a message, the PDU is the message itself. Modbus requests can be sent via two communication layers, RTU or TCP/IP. The ADU for these layers differs. But the PDU, the message, always has the same strcuture, regardless of the way it's transported. PDU === .. automodule:: umodbus.functions ADU for TCP/IP requests and responses ===================================== .. automodule:: umodbus.client.tcp .. _MODBUS Messaging on TCP/IP Implementation Guide V1.0b: http://modbus.org/docs/Modbus_Messaging_Implementation_Guide_V1_0b.pdf .. _MODBUS Application Protocol Specification V1.1b3: http://modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf ADU for RTU requests and responses ================================== .. automodule:: umodbus.client.serial.rtu .. _MODBUS over Serial Line Specification and Implementation Guide V1.02: http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf