MODBUS APPLICATION PROTOCOL SPECIFICATION V1

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April 26, 2012 1/50 MODBUS APPLICATION PROTOCOL SPECIFICATION CONTENTS 1 Introduction ........................................ ........................................ ...................................... 2 Scope of this document ........................................ ........................................ ........... 2 2 Abbreviations ........................................ ........................................ ................................... 2 3 Context ........................................ ........................................ ........................................ ..... 3 4 General description ........................................ ........................................ .......................... 3 PROTOCOL description.

The size of the MODBUS PDU is limited by the size constraint inherited from the first MODBUS implementation on Serial Line network (max. RS485 ADU = 256 bytes). Therefore: MODBUS PDU for serial line communication = 256 - Server address (1 byte) - CRC (2 bytes) = …

  Applications, Specification, Protocol, Ombud, Modbus application protocol specification