IECUNITS.DBF

- IEC protocol provides 3 levels of addressing - link address, common address and IOA address.

Scenario 1:

In the case of a common (ASDU) address being the same as the link address, then you dont need to use the IECUNITS.DBF.

And Citect IODevice address = ASDU Address.

Scenario 2:

If the link address is differnet to common address (ASDU address) then you need to use the IECUNITS.DBF to configure the address mapping.

Configuration Steps:

Enable the following citect.ini parameters:

[IEC870IP]
AddrConfigFileName = C:\\Citect\\V7\\Data\\Ieunits.dbf (this has to path where you have placed your IECioa.dbf file)
UseAddrConfigFile = 1

Modifying the IECUNITS.DBF:

E.g.-

Link Address - 2
Common address - 3

You need to add the following line to the IECUNITS.DBF
Index      LINKADDR       COMMADDR
20           2                      3

Index value 20 is an arbitary value and is used in the Citect's IODEVICE address form.

Note: I have attached a sample Iecunits.dbf file, which you can use to customize your project.