Title: 32 Pumper modbuss teknisk data.pdf.pdf
The Modbus data model states that registers numbered X are addressed in telegrams as X - 1, for example register 00104 (setpoint) is addressed as 00103 in a Modbus telegram.Note that CRC fields are not shown in the following examples.13.1 Modbus telegram overviewThe maximum size of a Modbus RTU telegram is 256 bytes. Telegrams must be separated by a silent interval of at least 3.5 character times.The standard Modbus RTU telegram format is shown in the table below.Slave addressFunction codeDataCRC1 byte1 byte0 to 252 bytes2 bytesA telegram starts with the slave address occupying one byte. Then comes a variable-size data field. For each telegram, a CRC is calculated and appended to the telegram, two bytes total. All bytes in the telegram, except for the CRC itself, are included in the check.Note that the CRC bytes are not shown in the examples in the following sections.13.2 Read holding registers, 0x03This function is used for reading holding registers from the slave.