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VTScadaLight - 0 Context & Reading Coils

Hi,

We have been unable to configure our ModbusTCP driver to 0 address offset. Can you please advise?
We did the following:
1) Make a Context Tag (which will be the parent of the TCP driver)
2) Go to Settings, and add a property: "ModiconTypedAddr1Offset". We set the value to 0.

We have also been unable to write to coils. Could you provide an example of how to write specific bits to a coil?

Thanks!

Hi, We have been unable to configure our ModbusTCP driver to 0 address offset. Can you please advise? We did the following: 1) Make a Context Tag (which will be the parent of the TCP driver) 2) Go to Settings, and add a property: "ModiconTypedAddr1Offset". We set the value to 0. We have also been unable to write to coils. Could you provide an example of how to write specific bits to a coil? Thanks!

Certain coil addresses will be point to discrete outputs which may be held in or out by logic in the PLC. I'd check for this type of conflict first. What devices are you trying to access and why would you need to set a 0 address offset when you can just add the offset to the addresses in the tags?

Certain coil addresses will be point to discrete outputs which may be held in or out by logic in the PLC. I'd check for this type of conflict first. What devices are you trying to access and why would you need to set a 0 address offset when you can just add the offset to the addresses in the tags?

Century Control Systems, Inc. www.centurycontrolsystems-inc.com

Unfortunately modbus register offsets are a perennial source of confusion.

Over the wire, the modbus protocol is 0-based for register addresses, but many modbus PLC configuration tools show registers as 1-based.

By default the VTScada Modbus driver I/O addresses are 1-based, the driver then subtracts the 1 when sending requests. If you want to use 0-based I/O addresses then there is a setting that allows this "ModiconTypedAddr1Offset", which you should set to 0 to allow 0-based I/O addresses.

See the help file section on Modbus Compatible Device I/O Addressing for more info.

Unfortunately modbus register offsets are a perennial source of confusion. Over the wire, the modbus protocol is 0-based for register addresses, but many modbus PLC configuration tools show registers as 1-based. By default the VTScada Modbus driver I/O addresses are 1-based, the driver then subtracts the 1 when sending requests. If you want to use 0-based I/O addresses then there is a setting that allows this "ModiconTypedAddr1Offset", which you should set to 0 to allow 0-based I/O addresses. See the help file section on [Modbus Compatible Device I/O Addressing](https://www.trihedral.com/help/Content/D_Tags/Dev_ModiconAddressing.htm) for more info.

Software Developer with Trihedral

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