Hanna Instruments HI520, Instruction Manual

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Operation Modes when using Modbus 14
4.3. RETRIEVING CONTROLLER PARAMETERS
1. Ensure HI520 is correctly configured for remote communication and RemLink or RemEdit have not timed out.
`
Controller is ready for reading data.
` 40195 and 40196 Modbus Holding Registers contain status and link information that is not password
protected.
2. Use function code Write Single Holding register (06) to set B1 in 40195 Holding Register i.e. enable
remote viewing.
` Controller settings are locked (view only) and cannot be changed remotely (or locally).
3. Use function code Read Holding register (03) to confirm the B1 has been set in 40195 Holding Register.
` Controller is in the Remote View mode.
4. Use Modbus function codes Read Coil (01), Read Input (02), Read Holding Register (03), or Read Input
Register (04) to read parameter values off the controller. See
Modbus Functions
for register details.
5. Repeat step 4 as needed.
`
Modbus Exception Codes may be encountered. See Exception Codes .
` Each transaction with the controller resets the timeout timer.
6. At the end of the process, use function code Write Single Holding Register (06) to clear B1 from 40195
Holding Register and disable remote viewing (allow local editing).
`
Stopping Modbus server communication with the controller until the link timeout expires, causes the
Remote View mode to exit.
7. Use function code Read Holding Register (03) to confirm the B1has been cleared from 40195 Holding Register.
` Confirmation that controller exited Remote View mode.
4.4. EDITING & SAVING CONTROLLER PARAMETERS
1. Ensure HI520 is correctly configured for remote communication and RemLink or RemEdit have not timed out.
` controller is ready for reading data
`
40195 and 40196 Modbus Holding Registers contain status and link information that is not password
protected
2. Use function code Write Single Holding Register (06) to set B1 and B2 in 40195 Holding Register i.e.
enable remote editing.
`
A copy of the controller’s settings is made and it should be saved before exiting the Remote Edit mode
(any changes will be lost).
`
Subsequent Modbus read/write transactions are with this copied image
3. Use function code Read Holding Register (03) to confirm B1 and B2 have been set in 40195 Holding Register.
`
Confirms the controller is in the Remote Edit mode.
4. Use correct Modbus function codes to read and write parameters. See
Modbus Functions
sections for details.
5. Repeat Step 4 as needed.
`
Controller could return Modbus Exception Codes. See Exception Codes .
` Each transaction with the controller resets a timeout timer.