Using Modbus Alias Addresses with the Triconex Ethernet Driver

I want to use the Modbus addresses that have been assigned to my Bin.Offset addresses in my Triconex Trident processor for communications using the TOP Server Triconex Ethernet driver.  However, when I use the Modbus address that I have assigned to my Bin.Offset address, it is not giving me the correct value that should be set for that Bin.Offset address.

The driver says that it supports Modbus aliases, so how do I configure my TOP Server project to take advantage of this feature?

In order to use the Modbus alias addresses assigned to the Bin.Offset addresses in your Triconex processor, the Modbus aliases must be assigned sequentially to a pre-defined range of Bin.Offset addresses in order for TOP Server to be able to successfully use the Modbus aliases.

For example:

1. 00001 and 0:0 both address the same BOOL output
2. 00002 and 0:1 both address the same BOOL output
3. 30001 and 4:0 both address the same REAL input
4. 30002 and 4:1 both address the same REAL input

So you can see, a specific Modbus Alias has to always be assigned to a specific Bin.Offset address in order for TOP Server to make use of this functionality.

Triconex Trident Controllers

With Triconex Trident controllers, the memory mapping functionality has been changed by the manufacturer from when this driver was originally enhanced with the ability to use Modbus Aliases.  Trident memory now maps Bin.Offset addresses to any empty space in contiguous memory, preventing the user from specifying a contiguous block of Bin.Offset addresses and assigning the corresponding Modbus Alias.

For example:

If you assigned 30001 to Bin.Offset 4:0, as in the example above, if someone removed the tag corresponding to Bin.Offset 4:0 and added it back, the Bin.Offset would change based on the available memory location where that tag was created again.

As such, the only way to use Modbus aliasing with Trident processors is to export the tag list from the TriStation project, format that into the correct CSV import format for TOP Server, using the Modbus address as the Tag Name in TOP Server.  This export/import procedure would have to be performed every time a change is made to the Trident program.

If you were to just use the Modbus addresses you have assigned in the TriStation project, you would actually be accessing the pre-defined Bin.Offset addresses that correspond to those Modbus aliases and not the actual Bin.Offset addresses you mapped in your project.

This is because the aliasing is performed in the TOP Server and the actual request sent to the device contains the Bin.Offset address.  This allows TOP Server to use the native TSAA protocol for communications and is why the Triconex Ethernet driver provides such fast performance.

Triconex Tricon Controllers

With Triconex Tricon controllers, when a Modbus Alias is used in the TriStation project, it is always mapped to the correct specific Bin.Offset address.  As such, if you are using a Triconex Tricon controller, you will be able to use the Modbus Aliases as if you were using the Bin.Offset addresses.