Proline Promass 83E/F/O Modbus RS485 Operating Instructions

Proline Promass 83 Modbus RS485Operation5.5.3 Modbus function codesThe function code determines which read, write and test operations should be executed by meansof the Modbus protocol. The measuring device supports the following function codes:FunctioncodeName in accordancewith ModbusspecificationDescription03 READ HOLDINGREGISTERReads one or more registers of the Modbus slave.1 to a maximum of 125 consecutive registers(1 register = 2 byte) can be read with a telegram.Application:For reading measuring device parameters with read and write access,such as reading the batch quantity.04 READ INPUT REGISTER Reads one or more registers of the Modbus slave.1 to a maximum of 125 consecutive registers(1 register = 2 byte) can be read with a telegram.Application:For reading measuring device parameters with read access, such asreading the measured values (mass flow, temperature, etc.).06 WRITE SINGLEREGISTERSWrites a single slave register with a new value.Application:For writing just one measuring device parameter, such as writing thebatch quantity or resetting the totalizer.! Note!Function code 16 is used for writing several registers by means of justone telegram.08 DIAGNOSTICS Checks the communication connection between the master and slave.The following "diagnostics codes" are supported:• Sub-function 00 = Return query data (loopback test)• Sub-function 02 = Return diagnostics register16 WRITE MULTIPLEREGISTERSWrites several slave registers with a new value.A maximum of 120 consecutive registers can be written with atelegram.Application:For writing several measuring device parameters, such as writing thebatch quantity and resetting the totalizer.!Note!23 READ/WRITEMULTIPLE REGISTERSSimultaneous reading and writing of 1 to max. 118 registers in atelegram. Write access is executed before read access.Application:For writing and reading several measuring device parameters, such aswriting the batch quantity and the correction quantity and reading thetotalizer value.• Broadcast messages are only permitted with function codes 06, 16 and 23.• The measuring device does not differentiate between function codes 03 and 04. These codes havethe same result.5.5.4 Maximum number of writesIf a nonvolatile device parameter is modified via the Modbus function codes 06, 16 or 23, thischange is saved in the EEPROM of the measuring device.The number of writes to the EEPROM is technically restricted to a maximum of 1 million. Attentionmust be paid to this limit since, if exceeded, it results in data loss and measuring device failure. Forthis reason, avoid constantly writing nonvolatile device parameters via the Modbus!Issue/Rev. 0.2 (12/12) MN0M030 • Page 45