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<< Click to Display Table of Contents >> Modbus RTU and Modbus TCP |
  
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<< Click to Display Table of Contents >> Modbus RTU and Modbus TCP |
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If the instrument you are using uses the Modbus protocol then you will need to know how the instrument is configured.
For instruments using Serial Comms:
When setting up the instrument itself :
| • | If there is a choice between Modbus or J-Bus protocol then choose J-BUS |
| • | If there is a choice for Data Bits choose 8 (EIGHT) |
| • | If there is a choice for Parity choose NONE |
| • | If there is a choice for Stop Bits choose 1 (ONE) |
Then in SpecView use the Add/Rename Instrument box to reflect the instrument's own settings:
On the Parity drop-down, ideally leave it as 'Driver' to use the driver defaults of '8N1', otherwise choose accordingly:
The meanings are listed below:
To define a Modbus instrument in SpecView:
Slave Address:
The two-digit address of the instrument in decimal.
Decimal places:
The number of decimal places for user defined items 0 / 1 / 2 / 3, SpecView will put a decimal place in the position indicated by this setting. The setting affects those variables where the number of decimals required is based on an instrument setting such as the range that has been selected. Some items, such as Output Power are fixed at a given number of decimal places and are not affected by this setting.
SpecView's Instrument Auto-Detection may assume 0 decimal places when detecting instruments. This might result in values being 10 or 100 times too large on displays.
Offset:
Some instrument companies (of, for example, multi-loop controllers) use an address structure so that a particular loop can be accessed with the appropriate address offset. This feature is also used with SpecView's 'Generic Modbus' instrument views. The addresses for each instance of the instrument are the same and offset by a fixed number. See Generic Modbus for more details. Also, where this feature is required for a specific instrument, refer to the Help for that instrument.
Extra:
Leave this field blank unless otherwise directed by your SpecView representative.
For Instruments using Modbus TCP/IP
To specify a Modbus TCP instrument choose 'TCP/IP' from the COM port drop-down list and enter the IP address or hostname into the box:
Port:
The port is by default 502, only change this if absolutely necessary.
For Slave Address, Decimal Places, Offset and Extra see above.
Also ensure the instrument variables are using the correct scaling.