Applies To:
  • CitectSCADA 5.xx

The Allen-Bradley ControlLogix can act as a simple gateway, or as a PLC. As a gateway, it is a product that lets users bridge and/or route information through the Allen-Bradley ControlNet, Ethernet and Data Highway Plus networks. As a PLC, the ControlLogix provides the same functionality as the gateway, plus the normal PLC functionality. How can Citect be used in conjunction with the ControlLogix? 

There are three communications methods offered by the ControlLogix (ControlNet, Ethernet, and Data Highway Plus).

Data Highway Plus (DH+)

The ControlLogix supports DH+ using the 1756-DHRIO module. Citect can communicate to the ControlLogix using DH+. Communications via DH+ use Citect's standard DH+ drivers (ABTCP/CIKT, ABTCP/SSTAB, and ABRSLINX).

Ethernet (TCP/IP)

The Ethernet (TCP/IP) option provided by the ControlLogix uses the Allen-Bradley's EPIC protocol, via the 1756-ENET module. See KB article Q2352 for more details on the CSP and EPIC protocols. Citect's Ethernet (TCP/IP) driver for most AB processors, called ABTCP, uses the CSP protocol and cannot be used with the ControlLogix. The use of Citect's ABRSLINX driver, which supports the EPIC protocol, is therefore recommended for use with the ControlLogix. The Citect ABRSLINX driver requires the use of Rockwell Software's RSLinx OEM product (Version1.70.57 or later).


The ControlLogix supports ControlNet using the 1756-CNB and 1756-CNBR modules. ControlNet is currently supported by Citect's ABRSLINX driver, and indirectly using Citect's OPC Client driver. The Citect ABRSLINX driver requires the use of Rockwell Software's RSLinx OEM product. The Citect ABRSLINX driver is available from Ci Technologies FTP site, or from Citect Support. The Citect OPC client driver can be used to communicate using ControlNet via the OPC standard using the SST ControlNet card. Contact SST for more information on SST's ControlNet & OPC solutions.

See also KB article Q2223.

Notes on ControlLogix PLC Support

1. To support the ControlLogix PLC functionality with Citect's current drivers, you must use the ControlLogix's "PLC-5 emulation mode".

2. Support of the ControlLogix PLC's native tag-based addressing is due mid-1999. This will coincide with Citect's support of Allen-Bradley's newest protocols which support the 'Producer - Consumer' model. Using Allen-Bradley's older protocols (such as CSP)   that do not support their new 'Producer - Consumer' model will have a significant impact on driver performance.